Lithium ion battery electrolyte additive and electrolyte

Abstract

The invention relates to a lithium ion battery electrolyte additive 2, 4-dicarboxamido sulfonyl cyclobutanone and a corresponding high-temperature lithium ion battery electrolyte. The electrolyte comprises the following components: lithium salt, an anhydrous organic solvent and an electrolyte additive; wherein the electrolyte additive comprises 2, 4-dicarboxamido sulfonyl cyclobutanone, and the electrolyte additive comprises 2, 4-dicarboxamide sulfonyl cyclobutanone; the use amount of the 2, 4-dicarboxamido sulfonyl cyclobutanone in the electrolyte is 0.1%-10% of the total mass of the electrolyte. The high-temperature lithium ion battery electrolyte added with 2, 4-dicarboxamidosulfonyl cyclobutanone can improve the high-temperature discharge performance, the high-temperature charge performance, the high-temperature cycle performance and the safety performance of a lithium ion battery when the lithium ion battery works at 4.2 V, does not influence the first efficiency and the rate capability, and has a relatively good application prospect in a high-temperature system.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, in particular to a high-temperature lithium ion battery electrolyte, and more particularly to 2,4-diformamidosulfonylcyclobutanone and an application thereof in the electrolyte. Background Art

[0002] Lithium-ion batteries have been widely used in many fields due to their many advantages, such as high energy density and long cycle life. However, with the expansion of application scenarios, especially the application needs in high-temperature environments, higher requirements are placed on lithium-ion battery electrolytes.

[0003] Lithium-ion batteries face a series of problems in high-temperature environments. First, conventional organic solvents and lithium salts in electrolytes have poor thermal stability. Organic solvents are easy to volatilize, which will not only change the composition and properties of the electrolyte, but also cause changes in the internal pressure of the battery, causing safety hazards. At the same time, lithium salts may decompose at high temperatures to produce some substances that are harmful to battery performance, such as increasing the internal resistance of the battery, affecting the battery's charge and discharge performance and cycle life. In addition, high temperatures will accelerate side reactions between electrode materials and electrolytes. For example, transition metal elements in the positive electrode material may dissolve and react with the electrolyte, further deteriorating battery performance, and may even cause thermal runaway of the battery, causing fires, explosions and other serious safety accidents.

[0004] In order to solve the problem of battery performance under high temperature environment, researchers have added some substances to the electrolyte to improve the high temperature stability of the battery. However, these additives often have some limitations that are difficult to overcome. In terms of improving the high temperature stability of the battery, some additives prevent the electrode material from directly contacting the electrolyte by forming a protective film on the surface of the electrode, thereby reducing the occurrence of side reactions. However, while these additives play a protective role, they bring other problems. On the one hand, they tend to reduce ionic conductivity. This is because the additives may interact with lithium ions or change the solvation structure of the electrolyte, making it difficult for lithium ions to migrate in the electrolyte. On the other hand, these additives also lead to higher film formation impedance. Although the protective film formed on the surface of the electrode can play a protective role, it is often dense, which will hinder the lithium ions from passing through the membrane for the charge and discharge process, thereby increasing the film formation impedance. This higher film formation impedance will lead to increased energy loss of the battery during the charge and discharge process, reducing the efficiency of the battery.

[0005] In summary, the additives used in existing high-temperature electrolytes to improve the high-temperature stability of batteries cannot simultaneously meet the requirements of improving high-temperature stability while ensuring ionic conductivity and low film formation impedance. This has prompted researchers to continuously explore new electrolyte systems and additives to achieve high-performance applications of lithium-ion batteries in high-temperature environments.

[0006] In response to the above technical problems, the prior art is to add high-temperature additives to the electrolyte, which plays a corresponding role, but also brings corresponding performance risks, as described below: (1) It may interact with lithium salts, change the dissociation state of lithium salts, affect the transmission of lithium ions, and thus have an adverse effect on the rate performance of the battery. (2) It may react with the organic solvent in the electrolyte, affecting the performance of the organic solvent, such as changing its wettability to the electrode material, thereby affecting the performance of the battery. (3) The additive may decompose itself or react with other components in the electrolyte as time and temperature change. The small molecules produced by decomposition may affect the ionic conductivity of the electrolyte, increase the internal resistance of the battery, and increase the energy loss during the charge and discharge process. (4) It may react with the electrode material, change the surface chemical state of the electrode material, affect the insertion and extraction efficiency of lithium ions, and gradually reduce the charge and discharge capacity of the battery. (5) If the addition amount is not accurate, it may cause a large change in the viscosity of the electrolyte. Too high viscosity will reduce the diffusion rate of lithium ions in the electrolyte, affecting the fast charging performance of the battery. It may also deteriorate the performance of the battery in a low temperature environment, because high viscosity electrolytes make ion migration more difficult at low temperatures. (6) If the content of certain additives is too high, the SEI film may become too thick. An overly thick SEI film will increase the battery impedance, making it difficult for the battery to dissipate heat at high temperatures, affecting the high temperature performance and high temperature stability of the battery. At the same time, an overly thick SEI film may change its own physical and chemical properties at high temperatures, reduce its ability to inhibit electrolyte decomposition, and be detrimental to the high temperature stability of the electrolyte. An overly thick SEI film will also hinder the transmission of lithium ions and reduce the ion transmission rate, thereby affecting the battery's charge and discharge performance and ion transmission performance. (7) Some additives may form an uneven film on the electrode surface, hindering the transmission of lithium ions on the electrode surface, affecting the battery's charge and discharge capacity and cycle life.

[0007] The present invention aims to solve the technical problems faced by high-temperature lithium-ion battery electrolytes, mainly involving the following aspects: (1) Improving thermal stability: Designing organic solvents with higher thermal stability is the key. Traditional organic solvents are easy to volatilize and decompose at high temperatures, resulting in decreased battery performance and safety hazards. It is necessary to develop or screen out organic solvents that can remain stable in high temperature environments, such as some cyclic organic solvents with special structures, whose chemical bond energy and molecular structure enable them to withstand higher temperatures without decomposition or volatilization. Design additives with high-temperature stability functions. These additives should be able to form a stable protective film on the electrode surface to prevent the electrode material from reacting with the electrolyte at high temperatures. At the same time, the additives themselves should have good chemical stability at high temperatures and will not decompose or react adversely with other components. For example, some amide-containing and sulfonyl-containing compounds can be used as high-temperature additives, which can improve the stability of the electrode surface film by chemical bonding and other means. (2) Guarantee of ionic conductivity: The selection of additives and solvents should take into account the impact on the microstructure of the electrolyte. To avoid the obstruction of lithium ion conduction channels due to the addition of additives, it is necessary to study how to maintain a good microstructure of the electrolyte by adjusting the molecular structure and concentration of the additives and selecting a suitable solvent combination to ensure that lithium ions can move quickly in it and maintain a high ionic conductivity. Ensure that the dissociation state of lithium salts in the electrolyte is good. Some additives may interact with lithium salts and affect the dissociation of lithium salts, thereby reducing ionic conductivity. Therefore, it is necessary to study how to avoid this adverse effect, or to promote the dissociation of lithium salts by adding specific substances so that lithium ions can be smoothly released from lithium salts and participate in the battery charging and discharging process. (3) Membrane impedance control: For the protective film formed on the electrode surface, its performance needs to be optimized. On the one hand, it is necessary to ensure that the formation of the film can effectively prevent direct contact between the electrode material and the electrolyte and reduce side reactions; on the other hand, it is necessary to control the density of the membrane to avoid the membrane being too dense, which will cause difficulties in lithium ion transmission and increase membrane impedance. The performance of the protective film can be optimized by adjusting the type and amount of additives and studying the formation mechanism of the membrane. (4) Comprehensive balance of battery performance: While improving high-temperature performance, the impact on low-temperature performance of the battery should be considered. Some measures taken to improve high-temperature performance may have an adverse effect on low-temperature performance. For example, some additives may increase the viscosity of the electrolyte, resulting in difficulty in ion migration at low temperatures. Therefore, it is necessary to study how to maintain or improve the low-temperature performance of the battery while improving high-temperature performance, such as by selecting a suitable combination of additives, or adjusting the amount of additives to achieve a balance between high-temperature and low-temperature performance; ensure the cycle life and safety performance of the battery; the cycle life of the battery may be affected in a high-temperature environment, such as the intensification of side reactions between electrode materials and electrolytes, and the increase of membrane impedance. At the same time, safety performance is also crucial, and it is necessary to prevent dangerous situations such as thermal runaway of the battery at high temperatures.The battery cycle life and safety performance can be guaranteed by optimizing the composition of the electrolyte, including the selection and matching of lithium salts, solvents and additives, as well as improving the battery structure and manufacturing process. Summary of the invention

[0008] The present invention aims at the deficiencies in the prior art and provides a lithium ion battery electrolyte additive and application thereof.

[0009] The invention provides a lithium ion battery electrolyte additive, wherein the additive is 2,4-diformamidosulfonylcyclobutanone as shown in formula I.

[0010]

[0011] The synthesis method of the lithium ion battery electrolyte additive comprises the following steps: dissolving cyclobutanol, adding an acidic solution of potassium dichromate, stirring and reacting to obtain cyclobutanone after the mixture is completely separated and purified; dissolving sodium hydrosulfide to prepare a sodium thiolate solution; dissolving cyclobutanone to prepare a solution; adding sodium thiolate to the cyclobutanone solution under an inert gas atmosphere, heating and stirring the solution to react so that the carbon No. 3 in the cyclobutanone reacts with the sodium thiolate to undergo a nucleophilic substitution reaction, and the sulfur atom replaces the carbon No. 3 position; cooling, filtering and purifying to obtain 3-thiocyclobutanone; dissolving 3-thiocyclobutanone, adding hydrogen peroxide and acetic acid to react by stirring, and oxidizing the sulfur atom to sulfone. acyl group; post-treatment to obtain 3-(sulfonyl)cyclobutanone; dissolve 3-(sulfonyl)cyclobutanone, add triethylamine and oxalyl chloride thereto, stir the reaction under ice bath to activate the sulfonyl group; under inert gas atmosphere, add the activated solution to a pre-cooled methanol solution of ammonia; heat to room temperature and continue to stir the reaction to allow ammonia to attack the activated sulfonyl group, resulting in an aminolysis reaction to initially convert the sulfonyl group into an amino group; add formic acid to the reaction system, heat and stir the reaction to allow formic acid to react with the amino group to form a formamide group; after the reaction, cool the reaction solution and post-treat the compound 2,4-diformamidosulfonylcyclobutanone.

[0012] In the above reaction, further, the inert gas atmosphere in the reaction is nitrogen; an acidic solution of potassium dichromate is added, and the reaction is stirred at a temperature of 25-40°C; sodium hydrosulfide is dissolved in ethanol to prepare a sodium thiolate solution; sodium thiolate is added dropwise to the cyclobutanone solution and heated to 50-80°C and stirred for reaction; the activated solution is slowly added dropwise to a pre-cooled methanol solution of ammonia; formic acid is slowly added dropwise to the reaction system, and the reaction system is heated to 40-60°C and stirred for reaction.

[0013] Furthermore, the steps of cooling the reaction solution and then treating it to obtain the target compound 2,4-dicarboxamidosulfonylcyclobutanone are as follows: cooling the reaction solution to room temperature; performing reduced pressure distillation on the reaction solution to remove the solvent and low-boiling by-products; extracting the residue with ethyl acetate; washing the extract with saturated brine and drying with anhydrous sodium sulfate; and finally purifying the product by column chromatography to obtain the compound 2,4-dicarboxamidosulfonylcyclobutanone.

[0014] For example, the synthesis method of 2,4-dicarboxamidosulfonylcyclobutanone can be as follows:

[0015] Dissolve 50g of cyclobutanol in 200mL of dichloromethane; slowly add an acidic solution of potassium dichromate (dissolve 80g of potassium dichromate in 100mL of concentrated sulfuric acid); stir and react at a temperature of 25-40°C;

[0016] Reaction equation: C 4 H 8 O(cyclobutanol)→C 4 H 6 O(cyclobutanone)+H 2 O.

[0017] After the reaction is completed, separation and purification are carried out, such as extraction, washing, drying, distillation and the like to obtain cyclobutanone.

[0018] Dissolve 40g of sodium hydrosulfide in 150mL of ethanol to prepare a sodium thiolate solution; dissolve 40g of cyclobutanone in 150mL of tetrahydrofuran; slowly drop 120mL of the sodium thiolate solution into the cyclobutanone solution under a nitrogen atmosphere; heat the reaction system to 50-80°C and stir the reaction for a period of time to allow carbon No. 3 in the cyclobutanone to undergo a nucleophilic substitution reaction with the sodium thiolate, and the sulfur atom replaces the carbon No. 3 position.

[0019] Reaction equation: C 4 H 6 O(cyclobutanone)+NaSH→C 3 H 5 OS(3-thiocyclobutanone)+NaOH.

[0020] After the reaction is completed, the reaction system is cooled; the generated sodium hydroxide is removed by filtration; and the filtrate is subjected to distillation or column chromatography separation to purify 3-thiocyclobutanone.

[0021] Dissolve 35 g of 3-thiocyclobutanone in 120 mL of dichloromethane; add 80 mL of hydrogen peroxide (30% concentration) and 30 mL of acetic acid; stir and react at a temperature of 25-40° C. to oxidize the sulfur atom to a sulfonyl group.

[0022] Reaction equation: C 3 H 5OS(3-thiocyclobutanone)+H 2 O 2 / AcOH→C 3 H 5 O 2 S(3-(Sulfonyl)cyclobutanone).

[0023] After the reaction is completed, extraction, washing, drying and distillation are performed to obtain the target compound 3-(sulfonyl)cyclobutanone.

[0024] Take 30 grams of 3-(sulfonyl)cyclobutanone and 150 milliliters of dichloromethane, dissolve 3-(sulfonyl)cyclobutanone in dichloromethane; add triethylamine (20 milliliters) and oxalyl chloride (15 milliliters) to it, stir and react for 1-2 hours in an ice bath to activate the sulfonyl group. Under nitrogen, slowly drop the activated solution into a pre-cooled methanol solution of ammonia; the methanol solution of ammonia is 200 milliliters; after the dropwise addition is completed, heat to room temperature and continue to stir and react for 4-6 hours; at this time, ammonia will attack the activated sulfonyl group, undergo an aminolysis reaction, and initially convert the sulfonyl group into an amino group; slowly drop formic acid (30 milliliters) into the reaction system; heat the reaction system to 40-60°C, stir and react for 2-3 hours; during this process, formic acid will react with the amino group to form a formamide group; after the reaction is completed, cool the reaction solution to room temperature.

[0025] The reaction solution was subjected to reduced pressure distillation to remove the solvent and low-boiling by-products; the residue was extracted with ethyl acetate; the extract was washed with saturated brine and dried with anhydrous sodium sulfate; finally, the product was purified by column chromatography to obtain the target compound 2,4-dicarboxamidosulfonylcyclobutanone.

[0026] The invention relates to a high-temperature lithium-ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone. The components of the electrolyte include lithium salt, an anhydrous organic solvent and an electrolyte additive; wherein the electrolyte additive includes 2,4-diformamidosulfonylcyclobutanone; the amount of 2,4-diformamidosulfonylcyclobutanone in the electrolyte is 0.1%-10% of the total mass of the electrolyte, preferably 0.1%-5%, and further preferably 0.1%-2%.

[0027] The invention discloses a high-temperature lithium-ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone, wherein the additive accounts for 0.1% to 20% of the total mass of the lithium-ion battery electrolyte.

[0028] In addition to 2,4-diformamidosulfonylcyclobutanone, the other additives are selected from vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate, lithium difluorooxalate borate, succinic anhydride, 1,3-propylene sultone, tetravinylsilane, lithium difluorophosphate, tris(trimethylsilyl)phosphate, vinyl sulfate, lithium bis(oxalate borate), 1,2-bis(cyanoethoxy)ethane, lithium bis(oxalate difluorophosphate), lithium bis(trifluoromethanesulfonyl)imide , vinyl sulfite, glycerol tris-propionitrile ether, succinonitrile, adiponitrile, methylene disulfonate, vinyl carbonate, tripropargyl phosphate, pentafluoroethoxy cyclotriphosphazene, 1,3,6-hexanetricarbonitrile, cyclopentane sulfone, p-toluenesulfonyl isocyanate, lithium tetrafluoroborate, 4,4'-vinyl sulfate, phenyl trifluoromethanesulfonate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphite, trimethyl Phosphorus oxide, triethyl phosphite, tris(trimethylsilyl)borate, tri(2,2,2-trifluoroethyl) borate, 1,4-butane sultone, maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, heptafluorobutyric anhydride, triphenyl phosphate, triphenyl phosphite, tripropargyl phosphate, p-toluenesulfonyl isocyanate, hexamethyldisilazane, tetramethyldivinyldisiloxane, vinyltriethoxysilane, tetramethyltetravinyl At least one of cyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, methylvinyldiethoxysilane, allyltrimethylsilane, dicyclohexylcarbodiimide, 3-trimethylsilyl-2-oxazolidinone, trimethylsilyldiethylamine, N-methyl-N-(trimethylsilyl)trifluoroacetamide, trialenylpropyl isocyanurate, diethyl cyanomethylphosphonate, and 1,6-hexamethylenediisocyanate.

[0029] The invention relates to a high-temperature lithium ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone, wherein the concentration of lithium salt in the electrolyte is 0.8M-1.4M.

[0030] Preferably, the lithium salt is selected from at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0031] The invention relates to a high-temperature lithium ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone, wherein anhydrous organic solvent in the electrolyte accounts for 60% to 80% of the total mass of the lithium ion battery electrolyte.

[0032] Preferably, the anhydrous organic solvent comprises carbonate.

[0033] Preferably, the carbonate mainly includes at least one of propylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate and ethylene carbonate.

[0034] Beneficial Effects

[0035] In order to solve the technical problems faced by high-temperature lithium-ion battery electrolytes, improve thermal stability, ensure particle conductivity, control membrane impedance, and ensure the balance of battery comprehensive performance, the present invention prepares a 2,4-diformamidosulfonylcyclobutanone and uses it as a lithium-ion battery electrolyte additive. Under high temperature conditions, traditional organic solvents are easy to volatilize and decompose, and the 2,4-diformamidosulfonylcyclobutanone prepared by the present invention interacts with the organic solvent. It is combined with the organic solvent through intermolecular forces to enhance the interaction between the organic solvent molecules, making its structure more stable and reducing the possibility of volatilization and decomposition. At the same time, 2,4-diformamidosulfonylcyclobutanone contains amide groups and sulfonyl groups. The amide group has a strong polarity and can interact with the active sites on the electrode surface through hydrogen bonds and the like. The sulfonyl group has a high chemical stability and can resist decomposition at high temperatures. When the additives gather on the electrode surface, the amide group and the sulfonyl group work together to form a stable protective film. The amide group combines with the groups on the surface of the electrode material, with the sulfonyl group facing outward, forming a layer of "protective armor" to prevent the electrode material from reacting with the electrolyte at high temperatures. At the same time, the chemical bond energy and molecular structure of the additive itself make it chemically stable at high temperatures and will not easily decompose or produce adverse chemical reactions with other components.

[0036] In addition, the molecular structure of 2,4-diformamidosulfonylcyclobutanone is relatively regular and will not cause serious obstruction to the lithium ion conduction channel. Its molecular size and shape enable it to form an orderly arrangement with the solvent molecules in the electrolyte. It forms a structure similar to a "channel network" with the solvent molecules, ensuring that lithium ions can move quickly in it. This microstructure can be further optimized by adjusting its concentration. When the concentration is appropriate, it can fill some "gaps" between solvent molecules, but will not occupy the lithium ion conduction channel, thereby maintaining a good microstructure and ensuring ion conductivity. The functional groups in 2,4-diformamidosulfonylcyclobutanone will have a specific interaction with the lithium salt. The amide group will have a weak coordination effect with the cations (lithium ions) in the lithium salt. This coordination effect is not very strong and will not hinder the dissociation of the lithium salt like some bad additives. On the contrary, it may promote the release of lithium ions from the lithium salt to a certain extent. The presence of sulfonyl groups may change the local electric field distribution of the electrolyte, reduce the dissociation energy barrier of lithium salts, and facilitate the dissociation of lithium salts, thereby ensuring that lithium ions can smoothly participate in the charge and discharge process of the battery. When 2,4-dicarboxamidosulfonylcyclobutanone forms a protective film on the electrode surface, the ratio and distribution of its amide group and sulfonyl group may affect the performance of the membrane. After the amide group is combined with the electrode surface, the sulfonyl group and other parts can form an appropriate spatial structure in the membrane. By adjusting the amount of additives, the density of the membrane can be controlled. When the amount is appropriate, the membrane will not be too dense because groups such as sulfonyl groups can prevent excessive accumulation of the membrane. This membrane can effectively prevent direct contact between the electrode material and the electrolyte, reduce side reactions, and at the same time will not hinder the transmission of lithium ions, avoiding the problems of ion transmission difficulties and increased membrane impedance caused by the membrane being too dense.

[0037] What is even better is that when abnormal conditions such as thermal runaway occur, 2,4-dicarboxamidosulfonylcyclobutanone exerts a flame retardant effect in the following ways. On the one hand, it may decompose at high temperatures to produce some non-flammable gases, such as nitrogen and carbon dioxide, which can dilute the concentration of combustible components in the electrolyte and reduce the possibility of combustion. On the other hand, the substance may participate in the thermal decomposition reaction of the electrolyte, change the reaction path, reduce the heat generated by the reaction, and thus slow down or prevent the combustion of the electrolyte.

[0038] Experiments have shown that using 2,4-dicarboxamidosulfonylcyclobutanone as a high-temperature lithium-ion battery electrolyte additive for lithium-ion batteries can improve their high-temperature discharge performance, high-temperature charging performance, high-temperature cycle performance and safety performance during operation, while not affecting the initial efficiency and rate performance. It has a good application prospect in high-temperature systems.

[0039] The present invention has been described in detail above, but the above embodiments are only illustrative in nature and are not intended to limit the present invention. In addition, this article is not limited by any theory described in the above prior art or invention content or the following examples. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with examples. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed for the present invention.

[0041] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, methods in the art.

[0042] The additive is 2,4-dicarboxamidosulfonylcyclobutanone as shown in formula I.

[0043]

[0044] The synthesis method of 2,4-dicarboxamidosulfonylcyclobutanone is:

[0045] Dissolve 50g of cyclobutanol in 200mL of dichloromethane; slowly add an acidic solution of potassium dichromate (dissolve 80g of potassium dichromate in 100mL of concentrated sulfuric acid); stir and react at 40°C;

[0046] Reaction equation: C 4 H 8 O(cyclobutanol)→C 4 H 6 O(cyclobutanone)+H 2 O.

[0047] After the reaction is completed, separation and purification are carried out, such as extraction, washing, drying, distillation and the like to obtain cyclobutanone.

[0048] Dissolve 40g of sodium hydrosulfide in 150mL of ethanol to prepare a sodium thiolate solution; dissolve 40g of cyclobutanone in 150mL of tetrahydrofuran; slowly drop 120mL of the sodium thiolate solution into the cyclobutanone solution under a nitrogen atmosphere; heat the reaction system to 80°C and stir the reaction for a period of time to allow carbon No. 3 in the cyclobutanone to undergo a nucleophilic substitution reaction with the sodium thiolate, and the sulfur atom replaces the carbon No. 3 position.

[0049] Reaction equation: C 4 H 6 O(cyclobutanone)+NaSH→C 3 H 5 OS(3-thiocyclobutanone)+NaOH.

[0050] After the reaction is completed, the reaction system is cooled; the generated sodium hydroxide is removed by filtration; and the filtrate is subjected to distillation or column chromatography separation to purify 3-thiocyclobutanone.

[0051] Dissolve 35 g of 3-thiocyclobutanone in 120 mL of dichloromethane; add 80 mL of hydrogen peroxide (30% concentration) and 30 mL of acetic acid; stir the reaction at 40° C. to oxidize the sulfur atom to a sulfonyl group.

[0052] Reaction equation: C 3 H 5 OS(3-thiocyclobutanone)+H 2 O 2 / AcOH→C 3 H 5 O 2 S(3-(Sulfonyl)cyclobutanone).

[0053] After the reaction is completed, extraction, washing, drying and distillation are performed to obtain the target compound 3-(sulfonyl)cyclobutanone.

[0054] Take 30 grams of 3-(sulfonyl)cyclobutanone and 150 milliliters of dichloromethane, dissolve 3-(sulfonyl)cyclobutanone in dichloromethane; add triethylamine (20 milliliters) and oxalyl chloride (15 milliliters) to it, stir and react for 1-2 hours in an ice bath to activate the sulfonyl group. Under nitrogen, slowly drop the activated solution into a pre-cooled ammonia methanol solution; the ammonia methanol solution is 200 milliliters; after the dropwise addition is completed, heat to room temperature and continue to stir and react for 4-6 hours; at this time, ammonia will attack the activated sulfonyl group, undergo an aminolysis reaction, and initially convert the sulfonyl group into an amino group; slowly drop formic acid (30 milliliters) into the reaction system; heat the reaction system to 60°C, stir and react for 2-3 hours; during this process, formic acid will react with the amino group to form a formamide group; after the reaction is completed, cool the reaction solution to room temperature.

[0055] The reaction solution was subjected to reduced pressure distillation to remove the solvent and low-boiling by-products; the residue was extracted with ethyl acetate; the extract was washed with saturated brine and dried with anhydrous sodium sulfate; finally, the product was purified by column chromatography to obtain the target compound 2,4-dicarboxamidosulfonylcyclobutanone.

[0056] Example

[0057] The positive electrode active material of the lithium ion battery used in the embodiment of the present invention is a ternary material (LiNi 0.6 Co 0.2 Mn 0.2 O 4), artificial graphite is selected as the negative electrode material, and the amount of electrolyte used is 2.3±0.5g / Ah. A lithium-ion battery assembled with a high-temperature lithium-ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone is selected as an example, and a lithium-ion battery assembled with a conventional electrolyte not containing 2,4-diformamidosulfonylcyclobutanone is selected as a comparative example.

[0058] The specific steps for preparing the electrolyte in the glove box (H2O < 5ppm) are as follows:

[0059] (1) dehydrating an anhydrous organic solvent molecular sieve under the protection of nitrogen or inert gas to obtain an anhydrous organic solvent;

[0060] (2) adding an appropriate amount of lithium salt to an anhydrous organic solvent, stirring and cooling to obtain a mixed solution;

[0061] (3) Add appropriate amount of additives to the mixed solution to obtain 2000 g of electrolyte, which is placed in a fluorination bottle.

[0062] The positive electrode material of the lithium-ion battery is a ternary material (LiNi 0.6 Co 0.2 Mn 0.2 O 4 ), the negative electrode material is artificial graphite, the design capacity is 60Ah, and the injection volume is 2.3±0.5g / Ah.

[0063] The electrolyte formulation is shown in the following comparative examples or embodiments.

[0064] Comparative Example 1:

[0065] The anhydrous organic solvent used was: diethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 30:40:30; lithium salt: lithium hexafluorophosphate (LiPF 6 ).

[0066] Comparative Example 2:

[0067] The anhydrous organic solvent used was: diethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 30:40:30; lithium salt: 0.8 M lithium hexafluorophosphate (LiPF 6 ), with a concentration of 0.4 M lithium bis(fluorosulfonyl)imide (LiFSI).

[0068] Comparative Example 3:

[0069] The anhydrous organic solvent used was: diethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 30:40:30; lithium salt: 0.8 M lithium hexafluorophosphate (LiPF 6), with a concentration of 0.4M lithium bis(fluorosulfonyl)imide (LiFSI). Additives: 0.5% lithium difluorooxalatoborate, 0.5% lithium difluorophosphate, 0.3% lithium difluorobis(oxalatophosphate), 1% vinylene carbonate, 1% 1,3-propane sultone, 0.5% fluoroethylene carbonate, 1% vinyl sulfate, 0.5% tris(trimethylsilyl)phosphate, 0.5% methylene disulfonate (the above percentages are the percentages of the corresponding additives in the total mass of the lithium-ion battery electrolyte, the same below).

[0070] Embodiment 1:

[0071] The anhydrous organic solvent used was: diethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 30:40:30; lithium salt: 0.8 M lithium hexafluorophosphate (LiPF 6 ), with a concentration of 0.4M lithium bis(fluorosulfonyl)imide (LiFSI). Additives: 0.5% lithium difluorooxalatoborate, 0.5% lithium difluorophosphate, 0.3% lithium difluorobis(oxalatophosphate), 1% vinylene carbonate, 1% 1,3-propane sultone, 0.5% fluoroethylene carbonate, 1% vinyl sulfate, 0.5% tris(trimethylsilyl)phosphate, 0.5% methylene disulfonate, 8% 2,4-dicarboxamidosulfonylcyclobutanone.

[0072] Embodiment 2:

[0073] The anhydrous organic solvent used was: diethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 30:40:30; lithium salt: 0.8 M lithium hexafluorophosphate (LiPF 6 ), with a concentration of 0.4M lithium bis(fluorosulfonyl)imide (LiFSI). Additives: 0.5% lithium difluorooxalatoborate, 0.5% lithium difluorophosphate, 0.3% lithium difluorobis(oxalatophosphate), 1% vinylene carbonate, 1% 1,3-propane sultone, 0.5% fluoroethylene carbonate, 1% vinyl sulfate, 0.5% tris(trimethylsilyl)phosphate, 0.5% methylene disulfonate, 5% 2,4-dicarboxamidosulfonylcyclobutanone.

[0074] Embodiment 3:

[0075] The anhydrous organic solvent used was: diethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 30:40:30; lithium salt: 0.8 M lithium hexafluorophosphate (LiPF 6), with a concentration of 0.4M lithium bis(fluorosulfonyl)imide (LiFSI). Additives: 0.5% lithium difluorooxalatoborate, 0.5% lithium difluorophosphate, 0.3% lithium difluorobis(oxalatophosphate), 1% vinylene carbonate, 1% 1,3-propane sultone, 0.5% fluoroethylene carbonate, 1% vinyl sulfate, 0.5% tris(trimethylsilyl)phosphate, 0.5% methylene disulfonate, 1% 2,4-dicarboxamidosulfonylcyclobutanone.

[0076] The lithium ion batteries assembled in the above comparative examples and embodiments were tested at room temperature (25°C) and in the voltage range of 2.75-4.2V, with a 1 / 3C discharge test to determine the constant capacity. The 2C charge capacity (%) = 2C charge capacity / 1C discharge capacity, and the 3C discharge capacity (%) = 3C discharge capacity / 1C discharge capacity. The results are shown in Table 1:

[0077] Table 1 Short-term performance test

[0078]

[0079] The lithium-ion batteries assembled in the comparative example and the embodiment were tested for capacity at 1C discharge in the range of 45°C-55°C, with a voltage range of 2.75-4.2V. The gas production of the battery was observed, and the battery was disassembled after high-temperature discharge to observe the pole pieces. The results are shown in Table 2:

[0080] Table 2 High temperature discharge performance test

[0081]

[0082] The high temperature discharge performance test results show that Comparative Example 1 has the lowest discharge capacity, and there is obvious lithium precipitation and gas production, mainly because no additives are introduced; Comparative Example 2 is better than Comparative Example 1, because LiFSI has higher high temperature stability; Comparative Example 3 is worse than Comparative Example 2, because the introduction of film-forming additives can effectively improve SEI stability, but high impedance leads to lithium precipitation and gas production; but the above effects are not as good as Examples 1-3. Examples 1-3 have high discharge capacity, no lithium precipitation and no gas production, indicating that the additives of the present invention have good high temperature performance.

[0083] The lithium-ion batteries assembled in the comparative example and the embodiment were stored at 100% SOC for 7 days at 55°C, and the capacity retention rate and recovery rate were tested in the voltage range of 2.75-4.2V. The gas generation and lithium precipitation of the battery were observed, and the results are shown in Table 3:

[0084] Table 3 High temperature charging performance test

[0085]

[0086] The lithium-ion batteries assembled in the comparative example and the embodiment were placed in an environment of 45°C and cycled at 1C charge and 1C discharge to test the capacity retention rate with a voltage range of 2.75-4.2V. The lithium deposition of the batteries was observed, and the results are shown in Table 5:

[0087] Table 5 High temperature cycle performance test

[0088] 1000 laps 2000 laps 3000 laps 4000 laps 5000 laps Lithium Separation Gas production Comparative Example 1 25.3％ 15.3％ 0.0％ 0.0％ 0.0％ Lithium Separation Gas production Comparative Example 2 68.1％ 58.1％ 38.1％ 8.1％ 0.0％ Lithium Separation Gas production Comparative Example 3 86.5％ 76.5％ 56.5％ 26.5％ 0.0％ Lithium Separation Gas production Example 1 95.0％ 92.0％ 89.0％ 87.0％ 80.0％ No lithium precipitation No gas production Example 2 96.5％ 93.5％ 90.5％ 88.5％ 81.5％ No lithium precipitation No gas production Example 3 97.9％ 94.9％ 91.9％ 89.9％ 82.9％ No lithium precipitation No gas production

[0089] The lithium-ion batteries assembled in the above comparative examples and embodiments were subjected to a needle puncture test at 25°C and 100% SOC. The results are shown in Table 7:

[0090] Table 7 Acupuncture test

[0091] acupuncture Comparative Example 1 Fire Comparative Example 2 Fire Comparative Example 3 Fire Example 1 No fire Example 2 No fire Example 3 No fire

[0092] From the results, it can be seen that the high-temperature lithium-ion battery electrolyte with 2,4-dicarboxamidosulfonylcyclobutanone added to the electrolyte can improve its high-temperature discharge performance, high-temperature charging performance, high-temperature cycle performance and safety performance when working at 4.2V for lithium-ion batteries, while not affecting the initial efficiency and rate performance, and has a good application prospect in high-temperature systems.

[0093] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and essence of the claims of the present invention; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A lithium ion battery electrolyte additive, characterized in that: The additive includes 2,4-dicarboxamidosulfonylcyclobutanone as described in Formula I 2. A method for synthesizing a lithium ion battery electrolyte additive as claimed in claim 1, characterized in that: The steps include: The cyclobutanol is dissolved, and an acidic solution of potassium dichromate is added, and the mixture is stirred and reacted completely, and then separated and purified to obtain cyclobutanone; sodium hydrosulfide is dissolved to prepare a sodium thiolate solution; cyclobutanone is dissolved to prepare a solution; under an inert gas atmosphere, sodium thiolate is added to the cyclobutanone solution, heated and stirred for reaction, so that carbon No. 3 in the cyclobutanone undergoes a nucleophilic substitution reaction with sodium thiolate, and the sulfur atom replaces the carbon No. 3 position; 3-thiocyclobutanone is obtained after cooling, filtering and purification; 3-thiocyclobutanone is dissolved, and hydrogen peroxide and acetic acid are added for stirring and reaction, so that the sulfur atom is oxidized to a sulfonyl group; post-treatment is performed to obtain 3-(sulfonyl)cyclobutanone; 2,4-diformamidosulfonylcyclobutanone; dissolving 3-(sulfonyl)cyclobutanone, adding triethylamine and oxalyl chloride thereto, stirring the reaction under ice bath to activate the sulfonyl group; adding the activated solution to a pre-cooled methanol solution of ammonia under an inert gas atmosphere; heating to room temperature and continuing to stir the reaction to allow ammonia to attack the activated sulfonyl group, causing an aminolysis reaction to preliminarily convert the sulfonyl group into an amino group; adding formic acid to the reaction system, heating and stirring the reaction to allow formic acid to react with the amino group to form a formamide group; after the reaction, cooling the reaction solution and post-treating it to obtain the compound 2,4-diformamidosulfonylcyclobutanone.

3. A method for synthesizing a lithium-ion battery electrolyte additive as claimed in claim 2, further characterized in that the inert gas atmosphere in the reaction is nitrogen; an acidic solution of potassium dichromate is added and stirred to react at a temperature of 25-40°C; sodium hydrosulfide is dissolved in ethanol to prepare a sodium thiolate solution; sodium thiolate is added dropwise to a cyclobutanone solution and heated to 50-80°C and stirred to react; the activated solution is slowly added dropwise to a pre-cooled methanol solution of ammonia; formic acid is slowly added dropwise to the reaction system, and the reaction system is heated to 40-60°C and stirred to react.

4. A method for synthesizing a lithium-ion battery electrolyte additive as claimed in claim 2 or 3, further characterized in that the step of cooling the reaction solution and then treating it to obtain the target compound 2,4-diformamidosulfonylcyclobutanone is: cooling the reaction solution to room temperature; subjecting the reaction solution to reduced pressure distillation to remove the solvent and low-boiling by-products; extracting the residue with ethyl acetate; washing the extract with saturated brine and drying with anhydrous sodium sulfate; and finally purifying the product by column chromatography to obtain the compound 2,4-diformamidosulfonylcyclobutanone.

5. A lithium ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone, characterized in that: The components of the electrolyte include lithium salt, anhydrous organic solvent and electrolyte additives; wherein the electrolyte additive includes 2,4-diformamidosulfonylcyclobutanone; the amount of 2,4-diformamidosulfonylcyclobutanone in the electrolyte is 0.1%-10% of the total mass of the electrolyte.

6. A lithium ion battery electrolyte containing 2,4-dicarboxamidosulfonylcyclobutanone as claimed in claim 5, further characterized in that the amount of 2,4-dicarboxamidosulfonylcyclobutanone in the electrolyte is 0.1%-5% of the total mass of the electrolyte, and more preferably 0.1%-2%.

7. A lithium ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone as claimed in claim 5 or 6, characterized in that: The amount of the electrolyte additive accounts for 0.1% to 20% of the total mass of the lithium ion battery electrolyte.

8. A lithium ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone as claimed in claim 5 or 6, characterized in that: In addition to 2,4-diformamidosulfonylcyclobutanone, other additives are selected from vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate, lithium difluorooxalate borate, succinic anhydride, 1,3-propylene sultone, tetravinylsilane, lithium difluorophosphate, tris(trimethylsilyl)phosphate, vinyl sulfate, lithium bis(oxalate borate), 1,2-bis(cyanoethoxy)ethane, lithium bis(oxalate difluorophosphate), lithium bis(trifluoromethanesulfonyl)imide, Ethylene sulfite, glycerol trispropionitrile ether, succinonitrile, adiponitrile, methylene disulfonate, vinyl carbonate, tripropargyl phosphate, pentafluoroethoxy cyclotriphosphazene, 1,3,6-hexanetricarbonitrile, cyclopentane sulfone, p-toluenesulfonyl isocyanate, lithium tetrafluoroborate, 4,4'-vinyl sulfate, phenyl trifluoromethanesulfonate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphite, trimethoxy Phosphorus, triethyl phosphite, tris(trimethylsilyl)borate, tri(2,2,2-trifluoroethyl) borate, 1,4-butane sultone, maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, heptafluorobutyric anhydride, triphenyl phosphate, triphenyl phosphite, tripropargyl phosphate, p-toluenesulfonyl isocyanate, hexamethyldisilazane, tetramethyldivinyldisiloxane, vinyltriethoxysilane, tetramethyltetravinyl At least one of cyclotetrasiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, methylvinyldiethoxysilane, allyltrimethylsilane, dicyclohexylcarbodiimide, 3-trimethylsilyl-2-oxazolidinone, trimethylsilyldiethylamine, N-methyl-N-(trimethylsilyl)trifluoroacetamide, trialenylpropyl isocyanurate, diethyl cyanomethylphosphonate, and 1,6-hexamethylenediisocyanate.

9. A lithium ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone as claimed in claim 5 or 6, characterized in that: The concentration of the lithium salt in the electrolyte is 0.8M-1.4M; the lithium salt is selected from at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

10. A lithium ion battery electrolyte containing 2,4-diformamidosulfonylcyclobutanone as claimed in claim 5 or 6, characterized in that: The anhydrous organic solvent includes carbonate.

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