Preparation method of cyano siloxane for high-voltage electrolyte and cyano siloxane

Abstract

The invention provides a preparation method of cyano siloxane for a high-voltage electrolyte and cyano siloxane, and belongs to the technical field of lithium ion battery electrolyte additives. The preparation method of the cyano siloxane for the high-voltage electrolyte comprises the following steps: mixing a reactant A with a first organic solvent, adding the mixture into a mixed solution of a reactant B and a second organic solvent, carrying out two-stage temperature control reaction, and purifying to obtain the cyano siloxane, wherein the reactant A has the following chemical general formula: (CN)-(CH2) n-(OH); the reactant B has the following chemical general formula: (R1)-(R2)-Si-(CI) 2, and R1 and R2 are alkyl groups. The electrolyte additive can be applied to a high-voltage lithium ion battery electrolyte additive, cyano siloxane is preferentially reduced and decomposed on the surface of a negative electrode to help to form a stable SEI film, so that a solvent deintercalation phenomenon is reduced, irreversible capacity loss of primary circulation is reduced, and the electrolyte additive has excellent effects in the aspects of acid removal and water removal; and particularly, the material has very high potential application value in a silicon negative electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolyte additives for lithium-ion batteries, and particularly relates to a preparation method of cyanosiloxane for high-voltage electrolytes and cyanosiloxane. Background Art

[0002] As the current mainstream energy storage technology, lithium-ion batteries have been widely used in fields such as portable electronic devices and electric vehicles due to their advantages of high working voltage, long cycle life, low self-discharge rate, and no memory effect. With the development demand of lithium-ion batteries in the market, improving the energy density of batteries has become an important research and development direction. Increasing the battery voltage or the capacity of the positive and negative electrode materials can be used to improve the battery energy density, but under high voltage or high capacity conditions, the decomposition of the electrolyte will be accelerated, thereby affecting the cycle performance and service life of the battery.

[0003] Therefore, providing an electrolyte additive suitable for high voltage to effectively inhibit the decomposition of the electrolyte and improve the cycle performance of the battery under high voltage is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] Aiming at the technical problem that the decomposition of the electrolyte will be accelerated under high voltage or high capacity conditions when improving the battery energy density by increasing the battery voltage or the capacity of the positive and negative electrode materials, which in turn affects the cycle performance and service life of the battery, the present invention provides a preparation method of cyanosiloxane for high-voltage electrolytes and cyanosiloxane. The cyanosiloxane can be adapted to high voltage and silicon-carbon negative electrode systems, effectively inhibit the decomposition of the electrolyte, improve the cycle performance of the battery under high voltage, and enhance the high-temperature high-voltage cycle life and high-temperature storage performance of the battery.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a preparation method of cyanosiloxane for high-voltage electrolytes, comprising the following steps: after mixing reactant A with a first organic solvent, adding it to a mixed solution of reactant B and a second organic solvent, and performing a two-stage temperature-controlled reaction, followed by purification treatment to obtain cyanosiloxane; wherein, reactant A has the following chemical general formula: (CN)-(CH2) n -(OH); reactant B has the following chemical general formula: (R1)-(R2)-Si-(CI)2, and both R1 and R2 are alkyl groups.

[0006] In some embodiments, the two-stage temperature-controlled reaction specifically includes the following steps:

[0007] The first-stage temperature-controlled reaction: controlling the temperature of the reaction system to be -10°C - 5°C, slowly dropping the mixed solution of reactant A and the first organic solvent into the mixed solution of reactant B and the second organic solvent, and the dropping time is 4 - 8 hours;

[0008] Second-stage temperature-controlled reaction: After the dropping is completed, raise the temperature of the reaction system to 10°C - 50°C and keep it warm for 13 - 17 hours to allow the reaction to proceed fully.

[0009] In some of these embodiments, both two-stage temperature-controlled reactions are carried out under stirring conditions, and the stirring speed is set at 100 - 1000 revolutions per minute.

[0010] In some of these embodiments, the purification treatment step includes a rotary evaporation step and a vacuum distillation step. Among them, vacuum distillation is carried out with gradient temperature increase for rectification and purification.

[0011] In some of these embodiments, the gradient temperature increase includes the following steps: the temperature of the rectification column is lower than 80°C, and the heating rate is controlled at 6°C / min; the temperature of the rectification column is 80°C - 100°C, and the heating rate is controlled at 2°C / min; the temperature of the rectification column is 100°C - 130°C, and the heating rate is controlled at 2°C / min; the temperature of the rectification column is higher than 130°C, and the heating rate is controlled at 2°C / min until distillate flows out.

[0012] In some of these embodiments, the molar ratio of reactant A to reactant B is (1.8 - 2.5):1.

[0013] In some of these embodiments, the molar ratio of reactant A to the first organic solvent is 1:(1.5 - 3.5).

[0014] In some of these embodiments, the molar ratio of reactant B to the second organic solvent is 1:(1.8 - 2.6).

[0015] On the other hand, the present invention also provides a cyanosiloxane prepared by the preparation method of the cyanosiloxane for high-voltage electrolytes described above.

[0016] In some of these embodiments, the cyanosiloxane has the following structural formula:

[0017]

[0018] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0019] (1) In the steps of the preparation method of the cyanosiloxane for high-voltage electrolytes of the present invention, the reactants are dissolved in an organic solvent with a low dielectric constant, and a full reaction is carried out through two-stage temperature control. Compared with the solid-phase method, the contact and collision between reactant molecules will be more sufficient, the reaction is more complete, there is no need to add some substances to remove side reactions, the organic by-products are less, and the yield and purity of the obtained product are higher.

[0020] (2) The cyanopolysiloxane in the molecular structure of the present invention contains two cyano groups, which can effectively adapt to the high-voltage state and the silicon-carbon negative electrode. The unsaturated triple bond of the cyano group can effectively protect the film formation of the positive and negative electrodes; the silicon-oxygen bond in its backbone structure can improve the lithium-ion conduction performance, effectively reduce the battery impedance, and the silicon-oxygen bond has good viscosity and is easy to combine with metal ions, which can improve the lithium-ion conduction efficiency; the cyano group and the silicon-oxygen bond are easy to combine with H protons and have good acid and water removal functions. The cyanopolysiloxane is preferentially reduced and decomposed on the surface of the negative electrode to help form a stable SEI film, thereby reducing the solvent co-intercalation phenomenon and reducing the irreversible capacity loss in the first cycle. It has excellent effects in acid and water removal, especially has high application value in silicon negative electrodes. Description of the Drawings

[0021] Figure 1 It is the infrared spectrum diagram of dimethyldicyanosiloxane provided in Example 1 of the present invention;

[0022] Figure 2 It is the gas chromatogram of dimethyldicyanosiloxane provided in Example 1 of the present invention;

[0023] Figure 3 is Figure 2 the gas chromatography quantitative test result;

[0024] Figure 4 It is the 1H NMR spectrum diagram of dimethyldicyanosiloxane provided in Example 1 of the present invention;

[0025] Figure 5 It is the infrared spectrum diagram of dimethyldicyanosiloxane provided in Example 2 of the present invention;

[0026] Figure 6 It is the gas chromatogram of dimethyldicyanosiloxane provided in Example 2 of the present invention;

[0027] Figure 7 is Figure 6 the gas chromatography quantitative test result;

[0028] Figure 8 It is the infrared spectrum diagram of dimethyldicyanosiloxane provided in Example 3 of the present invention;

[0029] Figure 9 It is the gas chromatogram of dimethyldicyanosiloxane provided in Example 3 of the present invention;

[0030] Figure 10 is Figure 9 the gas chromatography quantitative test result. Detailed Embodiments

[0031] In order to more comprehensively understand the characteristics and technical content of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the following-described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments of the present invention. In the following technical description, for the convenience of explanation, multiple details are provided to provide a full understanding of the disclosed embodiments. However, one or more embodiments can still be implemented without these details. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope claimed by the present invention.

[0032] The embodiments of the present invention provide a preparation method of cyanosiloxane for high-voltage electrolytes and cyanosiloxane, which can be adapted to high-voltage and silicon-carbon negative electrode systems, effectively inhibit the decomposition of electrolytes, improve the cycling performance of batteries under high voltage, and enhance the high-temperature high-voltage cycling life and high-temperature storage performance of batteries. The cyanosiloxane of the present invention participates in the film-forming effect - constructing the CEI film skeleton: during charging, the cyano group can be adsorbed on the surface of the positive electrode active material through complexation to form the skeleton structure of the positive electrode material interface film (CEI film), which helps other effective components of the electrolyte to form a film on the positive electrode surface, stabilize the structure and composition of the CEI film, prevent the destruction of the positive electrode structure, and inhibit the oxidative decomposition of the electrolyte; for the silicon negative electrode, it can protect the negative electrode SEI film: the cyano group has a protective effect on the solid electrolyte interface film (SEI film) of the negative electrode, can reduce the damage of transition metals to the SEI film, and enable the negative electrode surface to obtain a more uniform and dense surface morphology feature, improving the safety of the battery during use; at the same time, the participation of the cyano group can reduce side reactions and gas generation; capture H protons: when an oxidative side reaction occurs in the electrolyte, the cyano group can preferentially capture H protons, thereby reducing the occurrence of side reactions; reduce gas generation: the inhibitory effect on battery side reactions can effectively reduce the gas generation of the battery, improving the safety and stability of the battery; not only that, the cyano group can also improve the stability of the electrolyte: due to its high electronegativity, the cyano group can be adsorbed on the positive electrode surface, reducing the contact surface between the electrolyte and the positive electrode, reducing the direct contact between the electrolyte and the positive electrode material, thereby improving the stability of the electrolyte and inhibiting its decomposition under high voltage; remove water and acid, remove moisture: the cyano group itself can react with H2O to generate amino groups, playing a role in removing water, reducing the water content in the electrolyte, and avoiding side reactions caused by moisture; remove HF: the cyano group has strong electronegativity and can react with HF generated by the decomposition of lithium salts in the electrolyte to remove it, preventing HF from causing interfacial damage to the positive electrode and the dissolution of transition metals, constructing a uniform CEI film, and improving the electrochemical stability of the positive electrode.

[0033] The embodiments of the present invention provide a preparation method of cyanosiloxane for high-voltage electrolytes, including the following steps:

[0034] After mixing reactant A with the first organic solvent, it is added to the mixed solution of reactant B and the second organic solvent. After two-stage temperature-controlled reaction, cyanosiloxane is obtained through purification treatment. Among them, reactant A has the following chemical general formula: (CN)-(CH2) n -(OH), reactant B has the following chemical general formula: (R1)-(R2)-Si-(CI)2, where R1 and R2 are both alkyl groups; the molar ratio of reactant A to reactant B is (1.8 - 2.5):1; the molar ratio of reactant A to the first organic solvent is 1:(1.5 - 3.5), preferably 2.1:1; the molar ratio of reactant B to the second organic solvent is 1:(1.8 - 2.6), preferably 1:2.1; both the first organic solvent and the second organic solvent include one or more of chloroform, DMSO, and DMC.

[0035] The chemical reaction equation of the above preparation method of the present invention is as follows:

[0036]

[0037] In the above preparation method of the present invention, the entire reaction system exists in a liquid-phase organic solvent. The reactants have more sufficient intermolecular contact and collision than in the solid-phase method, the reaction is more complete, and the temperature control reaction in the liquid-phase system is more sufficient and uniform. Therefore, the corresponding organic by-products are less, and the yield and purity are higher. The above preparation method of the present invention uses a liquid-phase synthesis method to dissolve the reactants in an organic solvent with a low dielectric constant, which can promote chemical reactions, increase the reaction rate, and reduce side reactions. There is no need to add other substances to remove side reaction products during the reaction process, and the low dielectric constant solvent can be reused after rotary evaporation, which can reduce costs and is environmentally friendly. Cyanosiloxane is synthesized through two-stage temperature-controlled reaction, and the by-products are extremely low. The acidic substances generated are absorbed by the tail gas, and the pickling substances can be recycled. The remaining acidic substances will volatilize by themselves with the change of temperature during the reaction process, which is environmentally friendly. The rotary evaporation and vacuum distillation methods are used for rectification and purification to obtain a high-purity target product. The preparation process is simple, the by-products are low, and the cost is low.

[0038] In the above preparation method of the present invention, cyanosiloxane is synthesized through two-stage temperature-controlled reaction, and the by-products are extremely low. The two-stage temperature-controlled reaction specifically includes the following steps:

[0039] The first-stage temperature-controlled reaction: Control the temperature of the reaction system to be -10°C - 5°C, and slowly dropwise add the mixed solution of reactant B and the second organic solvent to the mixed solution of reactant A and the first organic solvent. The dropping time is 4 - 6 hours;

[0040] The second-stage temperature-controlled reaction: Raise the temperature of the reaction system to 10°C - 50°C and keep it warm for 13 - 17 hours to make the reaction proceed fully.

[0041] In the two-stage temperature-controlled reaction step of the present invention, introducing nitrogen can carry out some light components and acids, inhibit side reactions, and reduce acidity. In the first-stage temperature-controlled reaction step of the present invention, slow dropping during the dropping process can make the reactants react completely, improve the product purity. If the dropping is too fast, the reaction will be incomplete and the yield will be low. Preferably, the dropping rate is 1-2 drops / second when dropping slowly; by controlling the temperature of the reaction system, it is beneficial to complete the reaction, increase the yield, and improve the product purity. In the second-stage temperature-controlled reaction step, since most of the reaction has occurred, by raising the temperature of the reaction system, the reaction can overcome the steric effect and activation energy, promote the forward reaction, and once again improve the yield and purity of the substance to reduce the occurrence of side reactions. Both two-stage temperature-controlled reactions are carried out under stirring conditions, and the stirring speed is set at 100-1000 revolutions per minute. Stirring throughout the process makes the reaction more complete, makes the reaction system heat evenly, and at the same time, a thermometer needs to be connected to measure the temperature to prevent abnormal temperature; preferably, the rotation speed is 200-350 revolutions per minute.

[0042] In the above preparation method of the present invention, the purification treatment steps include rotary evaporation and vacuum distillation. Most of the solvent can be separated out by rotary evaporation, reducing the pressure of subsequent vacuum distillation, accelerating the purification time, and at the same time reducing the contact time between the product and the moisture in the air to prevent hydrolysis; moreover, the outflow solvent after rotary evaporation can also be recycled, saving energy and environmental protection and reducing costs. In the rotary evaporation step, the initial pressure is set at 260 mmHg, and it is reduced to 220 mmHg after 20 minutes. Then, every 5 minutes, it is reduced by 20-30 mmHg until 50 mmHg, and the rotary evaporation is stopped when no more liquid is distilled out; after rotary evaporation, vacuum distillation is carried out. The temperature rise of the rectification column should not be too fast, and it is carried out in four-stage gradients for heating, slow first and then fast. The temperature of the rectification column is lower than 80 °C, and the heating rate is controlled at 6 °C / min; the temperature of the rectification column is 80 °C - 100 °C, and the heating rate is controlled at 2 °C / min; the temperature of the rectification column is 100 °C - 130 °C, and the heating rate is controlled at 2 °C / min; the temperature of the rectification column is higher than 130 °C, and the heating rate is controlled at 2 °C / min until distillate flows out.

[0043] In the above preparation method of the present invention, the operation is anhydrous throughout the process. The vacuum distillation step needs to be evacuated, and the temperature control should not be too fast. It is heated slowly in gradients. When the temperature no longer increases, the distillate is collected. There is less distillate in the early stage and more in the later stage. The early stage is mainly to remove water vapor to prevent hydrolysis during the rectification process. Taking the final distillate, a cyanosiloxane with extremely high purity can be obtained. The cyanosiloxane obtained by the above preparation method of the present invention has a yield of 60%-70% and a purity greater than 95%. It has a wide range of applications, especially in silicon-carbon anodes, as well as high voltage and impedance aspects, with extremely high application value.

[0044] The embodiment of the present invention also provides a cyanosiloxane, which is prepared by the above preparation method. The cyanosiloxane has the following structural formula:

[0045]

[0046] In the formula, both R1 and R2 are alkyl groups. The cyanopolysiloxane molecule structure of the present invention contains 2 "-CN", which is effectively adapted to the high-voltage state and the silicon-carbon negative electrode; the "Si-O" in the cyanopolysiloxane skeleton structure can improve the lithium-ion conduction performance and effectively reduce the battery impedance; the "-CN" and "Si-O" in the cyanopolysiloxane molecule structure are easy to combine with H protons, having a good function of removing acid and water. The cyanopolysiloxane preferentially reduces and decomposes on the surface of the negative electrode, helping to form a stable SEI film, thereby reducing the solvent co-intercalation phenomenon and reducing the irreversible capacity loss in the first cycle.

[0047] In the embodiment of the present invention, the cyanopolysiloxane is applied as an additive for the electrolyte of a high-voltage lithium-ion battery. The cyanopolysiloxane preferentially reduces and decomposes on the surface of the negative electrode, helping to form a stable SEI film, thereby reducing the solvent co-intercalation phenomenon and reducing the irreversible capacity loss in the first cycle. It has excellent effects in removing acid and water, and has high application value especially in silicon negative electrodes.

[0048] In order to introduce the preparation method, cyanopolysiloxane and its application of the cyanopolysiloxane for high-voltage electrolytes provided by the embodiments of the present invention more clearly and in detail, the following will be described in conjunction with specific embodiments.

[0049] Raw material preparation: 3-hydroxypropionitrile is a commercially available product with a purity of AR; dichlorodimethylsilane is a commercially available product with a purity of AR, 99%; dimethyl carbonate is a commercially available product with a purity of 99% and a water content of ≤50 ppm; nitrogen purity is 99.999%.

[0050] Example 1

[0051] The preparation method of the cyanopolysiloxane for high-voltage electrolytes in this example specifically includes the following steps:

[0052] Weigh 126.061 g of dichlorodimethylsilane and 225.195 g of dimethyl carbonate with an electronic balance in an anhydrous glove box, and add them to a double-layer glass reaction kettle for mixing; weigh 149.264 g of 3-hydroxypropionitrile and 450.390 g of dimethyl carbonate with an electronic balance in an anhydrous glove box, and add them to a constant-pressure dropping funnel for mixing;

[0053] Connect the nitrogen gas pipeline to the double - layer glass reactor, introduce nitrogen gas, which can carry out some light components and acids, inhibit side reactions, and reduce acidity; the two ports of the reactor are respectively connected to a thermometer sleeve and a constant - pressure dropping funnel, and the thermometer extends below the liquid level of the reactor. A mechanical stirrer is connected above the reactor directly, and the stirring paddle extends below the liquid level of the reactor. Under normal pressure, the stirring speed is set at 200 revolutions per minute. The gas outlet of the reactor is sealed with silicone oil to prevent moisture in the air from entering, and the gas path is connected with a rubber tube; slowly drop the mixed solution of 3 - hydroxypropionitrile and dimethyl carbonate into the mixed solution of dichlorodimethylsilane and dimethyl carbonate. The dropping time is 4 h, and the temperature of the reaction system is maintained at - 3°C during the dropping process. When the dropping is completed, turn off the nitrogen gas, heat the reactor to 30°C, and stir for 13 hours;

[0054] Pour the reaction product into a rotary evaporation flask, and carry out rotary evaporation in an oil bath at 100°C for 2 hours. The initial pressure is set at 260 mmHg, and it is reduced to 220 mmHg after 20 min. Then, every 5 min, it is reduced by 20 - 30 mmHg until 50 mmHg;

[0055] Carry out rectification and purification on the residue after rotary evaporation. Use a thimble - type rectification column, connect the condenser, thermometer and receiving flask, and carry out gradient heating: first slow and then fast. When the temperature of the rectification column is lower than 80°C, control the heating rate at 6°C / min; when the temperature of the rectification column is 80°C - 100°C, control the heating rate at 2°C / min; when the temperature of the rectification column is 100°C - 130°C, control the heating rate at 2°C / min; when the temperature of the rectification column is higher than 130°C, control the heating rate at 2°C / min until distillate flows out, and turn on the vacuum pump at 100°C, set the vacuum degree at 6.5×10 -3 Pa, take out the distillate at 135°C - 162°C and weigh it. The yield is 60%;

[0056] Carry out infrared testing on the obtained product. The peak areas of each group are clear. It is initially estimated that there are no by - products, and the purity detected by gas chromatography is 96.021%.

[0057] Example 2

[0058] The preparation method of the cyano - siloxane for high - voltage electrolytes in this example specifically includes the following steps:

[0059] Weigh 126.061 g of dichlorodimethylsilane and 225.195 g of dimethyl carbonate with an electronic balance in an anhydrous glove box, and add them to the double - layer glass reactor for mixing; weigh 149.264 g of 3 - hydroxypropionitrile and 450.390 g of dimethyl carbonate with an electronic balance in an anhydrous glove box, and add them to the constant - pressure dropping funnel for mixing;

[0060] Connect the nitrogen gas pipeline to the double-layer glass reactor, introduce nitrogen gas, which can carry out some light components and acids, inhibit side reactions, and reduce acidity; the two ports of the reactor are respectively connected to the thermometer sleeve and the constant pressure dropping funnel, and the thermometer extends below the liquid level of the reactor. A mechanical stirrer is connected above the reactor directly, and the stirring paddle extends below the liquid level of the reactor. Under normal pressure, the stirring speed is set at 300 revolutions per minute. The gas outlet of the reactor is sealed with silicone oil to prevent moisture in the air from entering, and the gas path is connected with a rubber tube; slowly drop the mixed solution of 3-hydroxypropionitrile and dimethyl carbonate into the mixed solution of dichlorodimethylsilane and dimethyl carbonate. The dropping time is 4 h, and the temperature of the reaction system is maintained at -3 °C during the dropping process. When the dropping is completed, turn off the nitrogen gas, heat the reactor to 30 °C, and stir for 13 hours. During the dropping process, introduce nitrogen gas, which can carry out some light components and acids, inhibit side reactions, and reduce acidity;

[0061] Pour the reaction product into a rotary evaporation flask, and carry out rotary evaporation in an oil bath at 100 °C for 2 hours. The initial pressure is set at 260 mmHg, and it is reduced to 220 mmHg after 20 min. Then, every 5 min, it is reduced by 20 - 30 mmHg until 50 mmHg;

[0062] Rectify and purify the residue after rotary evaporation. Use a thimble-type rectification column, connect the condenser, thermometer and receiving flask, and carry out gradient heating: slow first and then fast. When the temperature of the rectification column is lower than 80 °C, control the heating rate at 6 °C / min; when the temperature of the rectification column is 80 °C - 100 °C, control the heating rate at 2 °C / min; when the temperature of the rectification column is 100 °C - 130 °C, control the heating rate at 2 °C / min; when the temperature of the rectification column is higher than 130 °C, control the heating rate at 2 °C / min until distillate flows out, and turn on the vacuum pump at 100 °C, set the vacuum degree at 6.5×10 -3 Pa, take out the fraction at 140 °C - 162 °C and weigh it. The yield is 64%;

[0063] Carry out infrared test on the obtained product. The peak areas of each group are clear. It is preliminarily estimated that there are no by-products, and the purity detected by gas chromatography is 97.245%.

[0064] Example 3

[0065] The preparation method of the cyanosiloxane for high-voltage electrolyte in this example specifically includes the following steps:

[0066] Weigh 126.061 g of dichlorodimethylsilane and 225.195 g of dimethyl carbonate with an electronic balance in an anhydrous glove box, and add them to the double-layer glass reactor for mixing; weigh 149.264 g of 3-hydroxypropionitrile and 450.390 g of dimethyl carbonate with an electronic balance in an anhydrous glove box, and add them to the constant pressure dropping funnel for mixing;

[0067] Connect the nitrogen pipeline to the double-layer glass reactor, introduce nitrogen, which can carry out some light components and acids, inhibit side reactions, and reduce acidity. The two ports of the reactor are respectively connected to a thermometer sleeve and a constant-pressure dropping funnel, and the thermometer extends below the liquid level of the reactor. A mechanical stirrer is connected above the reactor directly, and the stirring paddle extends below the liquid level of the reactor. Under normal pressure, the stirring speed is set at 300 revolutions per minute. The gas outlet of the reactor is sealed with silicone oil to prevent moisture in the air from entering, and the gas path is connected with a rubber tube; slowly drop the mixed solution of 3-hydroxypropionitrile and dimethyl carbonate into the mixed solution of dichlorodimethylsilane and dimethyl carbonate. The dropping time is 7 hours, and the temperature of the reaction system is maintained at -3 °C during the dropping process. When the dropping is completed, turn off the nitrogen, heat the reactor to 30 °C, and stir for 13 hours;

[0068] Pour the reaction product into a rotary evaporation flask, and perform rotary evaporation in an oil bath at 100 °C for 2 hours. The initial pressure is set at 260 mmHg, and it is reduced to 220 mmHg after 20 minutes. Then, every 5 minutes, it is reduced by 20 - 30 mmHg until 50 mmHg;

[0069] Rectify and purify the residue after rotary evaporation. Use a thimble distillation column, connect the condenser, thermometer, and receiving flask, and heat it in a gradient manner, first slowly and then quickly. The temperature of the distillation column is lower than 80 °C, and the heating rate is controlled at 6 °C / min; when the temperature of the distillation column is 80 °C - 100 °C, the heating rate is controlled at 2 °C / min; when the temperature of the distillation column is 100 °C - 130 °C, the heating rate is controlled at 2 °C / min; when the temperature of the distillation column is higher than 130 °C, the heating rate is controlled at 2 °C / min until distillate flows out, and turn on the vacuum pump at 100 °C, and set the vacuum degree to 6.5×10 -3 Pa, take out the fraction at 140 °C - 168 °C and weigh it. The yield is 66%;

[0070] Perform infrared testing on the obtained product. The peak areas of each group are clear, and it is preliminarily estimated that there are no by-products. The purity detected by gas chromatography is 95.991%.

[0071] Comparative Example 1

[0072] The preparation method of cyanosiloxane in this comparative example specifically includes the following steps:

[0073] Weigh 126.061 g of dichlorodimethylsilane and 225.195 g of dimethyl carbonate at room temperature with an electronic balance, and add them to a double-layer glass reactor for mixing; weigh 149.264 g of 3-hydroxypropionitrile and 450.390 g of dimethyl carbonate in an anhydrous glove box with an electronic balance, and add them to a constant-pressure dropping funnel for mixing;

[0074] Connect the nitrogen pipeline to the double-layer glass reactor, introduce nitrogen, which can carry out some light components and acids, inhibit side reactions, and reduce acidity. The two ports of the reactor are respectively connected to a thermometer sleeve and a constant-pressure dropping funnel, and the thermometer extends below the liquid level of the reactor. A mechanical stirrer is connected above the reactor directly, and the stirring paddle extends below the liquid level of the reactor. The rotation speed is set to 200 revolutions per minute. The gas outlet is sealed with silicone oil, and the gas path is connected with a rubber tube. Slowly drop the mixed solution of 3-hydroxypropionitrile and dimethyl carbonate into the mixed solution of dichlorodimethylsilane and dimethyl carbonate without controlling the dropping speed. The dropping is completed in half an hour. Keep the temperature of the reaction system at -9°C. Close the nitrogen when the dropping is finished, and heat the reactor to 50°C and stir for 12 hours.

[0075] Pour the reaction product into a rotary evaporation flask, and rotary evaporate it in an oil bath at 100°C for 1 hour. The initial pressure is set to 260 mmHg, and it is reduced to 220 mmHg after 20 minutes. Then, every 5 minutes, it is reduced by 20 - 30 mmHg until 50 mmHg.

[0076] Rectify and purify the residue after rotary evaporation. Use a thimble-type rectification column, connect the condenser, thermometer, and receiving flask well, and heat up in a gradient manner, first slowly and then quickly. The temperature of the rectification column is below 80°C, and the heating rate is controlled at 6°C / min; when the temperature of the rectification column is 80°C - 100°C, the heating rate is controlled at 2°C / min; when the temperature of the rectification column is 100°C - 130°C, the heating rate is controlled at 2°C / min; when the temperature of the rectification column is above 130°C, control the heating rate at 2°C / min until distillate flows out, and turn on the vacuum pump at 100°C, set the vacuum degree to 6.5×10 -3 Pa, take out the distillate at 135°C - 162°C and weigh it. The yield is 42%.

[0077] Conduct infrared testing on the obtained product. The peak areas of each group are clear. It is preliminarily estimated that there are no by-products, and the purity detected by gas chromatography is 79.71%.

[0078] Comparative Example 2

[0079] The preparation method of cyanosiloxane in this comparative example specifically includes the following steps:

[0080] Weigh 126.061 g of dichlorodimethylsilane and 125.195 g of dimethyl carbonate at room temperature with an electronic balance and add them to the double-layer glass reactor for mixing; weigh 149.264 g of 3-hydroxypropionitrile and 350.390 g of dimethyl carbonate in an anhydrous glove box with an electronic balance and add them to the constant-pressure dropping funnel for mixing.

[0081] Connect nitrogen gas to a double-layer glass reactor. The two openings of the reactor are respectively connected to a thermometer sleeve and a constant-pressure dropping funnel, and the thermometer is inserted below the liquid level of the reactor. A mechanical stirrer is connected directly above the reactor, and the stirrer paddle is inserted below the liquid level of the reactor. Set the rotation speed to 300 revolutions per minute. Seal the gas outlet with silicone oil and connect the gas path with a rubber tube. Slowly add the mixed solution of 3-hydroxypropionitrile and dimethyl carbonate to the mixed solution of dichlorodimethylsilane and dimethyl carbonate over a period of 4 hours. During the addition process, maintain the temperature of the reaction system at -3°C. When the addition is complete, turn off the nitrogen gas, heat the reactor to 30°C, and stir for 13 hours.

[0082] Pour the reaction product into a rotary evaporation flask and perform rotary evaporation in an oil bath at 100°C for 2 hours.

[0083] Purify the residue after rotary evaporation by fractional distillation. Use a thimble-type fractionating column, connect the condenser, thermometer, and receiving flask, and gradually increase the temperature in a gradient manner, first slowly and then quickly. Keep the temperature of the fractionating column below 80°C and control the heating rate at 6°C / min; when the temperature of the fractionating column is 80°C - 100°C, control the heating rate at 2°C / min; when the temperature of the fractionating column is 100°C - 130°C, control the heating rate at 2°C / min; when the temperature of the fractionating column is above 130°C, control the heating rate at 2°C / min until distillate flows out, and turn on the vacuum pump at 100°C and set the vacuum degree to 6.5×10 -3 Pa, take out the fraction at 120°C - 170°C, weigh it, and the yield is 69%.

[0084] Perform infrared testing on the obtained product. The peak areas of each group are clear, and it is preliminarily estimated that there are no by-products. The purity detected by gas chromatography is 86.54%.

[0085] Comparative Example 3

[0086] The preparation method of cyanosiloxane in this comparative example specifically includes the following steps:

[0087] Weigh 126.061 g of dichlorodimethylsilane and 125.195 g of dimethyl carbonate at room temperature and add them to a double-layer glass reactor for mixing; weigh 149.264 g of 3-hydroxypropionitrile and 350.390 g of dimethyl carbonate in an anhydrous glove box and add them to a constant-pressure dropping funnel for mixing.

[0088] Connect the nitrogen gas pipeline to the double-layer glass reactor. The two ports of the reactor are respectively connected to the thermometer sleeve and the constant pressure dropping funnel. The thermometer is inserted below the liquid level of the reactor. A mechanical stirrer is connected directly above the reactor, and the stirring paddle is inserted below the liquid level of the reactor. The rotation speed is set to 300 revolutions per minute. The gas outlet is sealed with silicone oil, and the gas path is connected with a rubber tube. Slowly drop the mixed solution of 3-hydroxypropionitrile and dimethyl carbonate into the mixed solution of dichlorodimethylsilane and dimethyl carbonate. The dropping time is 1 h. During the dropping process, keep the temperature of the reaction system at -3 °C. When the dropping is completed, turn off the nitrogen gas, heat the reactor to 30 °C, and stir for 13 hours.

[0089] Pour the reaction product into a rotary evaporation flask, and carry out rotary evaporation in an oil bath at 100 °C for 2 h. Connect the condenser, thermometer and receiving flask during the rotary evaporation process, and carry out gradient heating: the initial pressure is set to 260 mmHg, and it is reduced to 220 mmHg after 20 min. Then, every 5 min, it is reduced by 20 - 30 mmHg until 50 mmHg. After the rotary evaporation is completed, do not carry out vacuum distillation. Weigh the remaining components after rotary evaporation, and the yield is 65%.

[0090] Carry out infrared testing on the obtained product. The peak areas of each group are clear. It is preliminarily estimated that there are no by-products, and the purity detected by gas chromatography is 12%.

[0091] The yields and purities of the products obtained in Examples 1 - 3 and Comparative Examples 1 - 3 are shown in Table 1.

[0092] Table 1 Yields and purities of the products obtained in Examples 1 - 3 and Comparative Examples 1 - 3

[0093]

[0094]

[0095] As can be seen from the above, compared with Examples 1 - 3, in Comparative Example 1, the rotary evaporation time is 1 h and the dropping time is half an hour, indicating that too short rotary evaporation time leads to incomplete purification, and short dropping time will affect the conversion rate of the synthesis reaction; in Comparative Example 2, the amount of solvent used for dichlorodimethylsilane is less, and dichlorodimethylsilane is not completely dissolved. The temperature range is increased during the purification process, and some light components are distilled out, resulting in a decrease in the purity of the distillate. This shows that when the amount of solvent decreases and the temperature range in the purification process is large, there are more impurities, and some of the early impurity fractions and the final heavy components are distilled out together, increasing the total yield but decreasing the purity; in Comparative Example 3, vacuum distillation is not carried out, indicating that only part of the impurities can be removed by the preliminary crude purification. To obtain a high-purity product, vacuum distillation is required for further purification.

[0096] The infrared spectrum of the product obtained in Example 1 is as shown in the appendix Figure 1 shown, the infrared spectrum of the product obtained in Example 2 is as shown in the appendix Figure 5 shown, the infrared spectrum of the product obtained in Example 1 is as shown in the appendixFigure 8 As shown, it can be seen from the figure that Figure 1 , Figure 5 and Figure 8 are basically the same, indicating that the same target product is obtained in Examples 1-3. Functional groups are determined according to the peak positions of the infrared spectrum. The 1H NMR spectrum infers the types of hydrogen atoms, the chemical environments they are in, and the connection ways between them in the organic compound through the peak positions (chemical shifts), the splitting of the peaks (coupling constants), and the peak areas in the spectrum diagram, so as to determine the molecular structure of the organic compound. Gas chromatography quantitatively characterizes the product purity. From the attached Figure 1 infrared spectrum diagram, it can be seen that the peak positions correspond to the main functional group positions as follows: methyl stretching vibration at 2960-2850 cm -1 , methylene stretching vibration at 2930-2850 cm -1 , cyano group (C≡N) at 2150-2280 cm -1 , Si-O-C stretching vibration doublet at 1400-1667 cm -1 , Si-O-C symmetric stretching vibration at 933-965 cm -1 . The characteristic peaks of the functional groups contained in the target product dimethyldicyanosiloxane can all be found in the attached Figure 1 infrared spectrum diagram, indicating the generation of the target product dimethyldicyanosiloxane in the infrared test.

[0097] The gas chromatography of the product obtained in Example 1 is as shown in the attached Figure 2 ; the gas chromatography quantitative test results are as shown in the attached Figure 3 ; the gas chromatography of the product obtained in Example 2 is as shown in the attached Figure 6 ; the gas chromatography quantitative test results are as shown in the attached Figure 7 ; the gas chromatography of the product obtained in Example 3 is as shown in the attached Figure 9 ; the gas chromatography quantitative test results are as shown in the attached Figure 10 ; the minimum temperature of vacuum distillation in Example 1 is slightly lower, so there are some light components in the gas chromatography; there are no light components but some heavy components in Example 2 when the temperature increases; the heavy components increase when the highest temperature increases in Example 3. From the attached Figure 3 it can be seen that for dimethyldicyanosiloxane, at 18.575 min, the peak area is 3288.4, the peak height is 821.9, the peak width is 0.0523, the peak area percentage is 96.021%, and the symmetry factor is 4.541; at 9.576 min, the peak area is 136.3, the peak height is 43.5, the peak width is 0.0446, the peak area percentage is 3.979%, and the symmetry factor is 0.385; from the attached Figure 7It can be seen that for dimethyldicyanosiloxane, at 18.577 min, the peak area is 3593.5, the peak height is 871.9, the peak width is 0.0561, the percentage of peak area is 96.975%, and the symmetry factor is 4.812; at 19.929 min, the peak area is 101.8, the peak height is 47.7, the peak width is 0.0329, the percentage of peak area is 2.747%, and the symmetry factor is 1.236; from the appendix Figure 10 It can be seen that for dimethyldicyanosiloxane, at 18.571 min, the peak area is 3394.4, the peak height is 831.2, the peak width is 0.0564, the percentage of peak area is 96.374%, and the symmetry factor is 4.616; at 19.927 min, the peak area is 127.7, the peak height is 63.3, the peak width is 0.0316, the percentage of peak area is 3.626%, and the symmetry factor is 1.155.

[0098] The nuclear magnetic resonance hydrogen spectrum of Example 1 is as shown in the appendix Figure 4 shown; from the appendix Figure 4 shown nuclear magnetic resonance hydrogen spectrum, the chemical shift of methyl (-CH3) hydrogen atoms is generally around 0 - 1.2 ppm. The cyano group (-CN) is an electron-withdrawing group, which will shift the chemical shift of adjacent hydrogen atoms to the low field. Therefore, the chemical shift of methyl in the nuclear magnetic resonance hydrogen spectrum is between 0 - 0.25 ppm. Usually, the chemical shift of methylene hydrogen connected to the cyano group is around 3 - 4 ppm. In cyanoethyl, due to the electron-withdrawing effect of the cyano group, the chemical shift of methylene hydrogen will be at the high field end of this range, and the chemical shift of methylene hydrogen is around 2.5 - 2.8 ppm. The chemical shift of the hydrogen atom connected to oxygen and methylene is 3.5 - 4.0 ppm, which is consistent with the chemical shift of hydrogen in dimethyldicyanosiloxane fitted by common professional chemical drawing software, proving that the target structure product is synthesized by the preparation method of the present invention.

[0099] Finally, it should be noted that: The present invention is not limited to the above-listed embodiments. The above are only preferred and feasible embodiments of the present invention. The above-described embodiments are only used to illustrate the technical solutions of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, modifications, evolutions, and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of cyanosiloxane for high-voltage electrolytes, characterized in that, It includes the following steps: After mixing reactant A with the first organic solvent, add it to the mixed solution of reactant B and the second organic solvent, and after two-stage temperature-controlled reaction, carry out purification treatment to obtain cyanosiloxane; among them, reactant A has the following chemical general formula: (CN)-(CH2) n -(OH); reactant B has the following chemical general formula: (R1)-(R2)-Si-(CI)2, where both R1 and R2 are alkyl groups.

2. The preparation method of the cyanosiloxane for high-voltage electrolytes according to claim 1, characterized in that, The two-stage temperature-controlled reaction specifically includes the following steps: The first-stage temperature-controlled reaction: Control the temperature of the reaction system to be -10°C - 5°C, and slowly dropwise add the mixed solution of reactant A and the first organic solvent to the mixed solution of reactant B and the second organic solvent. The dropping time is 4 - 6 hours; The second-stage temperature-controlled reaction: After the dropping is completed, raise the temperature of the reaction system to 10°C - 50°C and keep it warm for 13 - 17 hours to allow the reaction to proceed fully.

3. The preparation method of the cyanosiloxane for high-voltage electrolytes according to claim 1, characterized in that, Both the two-stage temperature-controlled reactions are carried out under stirring conditions, and the stirring speed is set to 100 - 1000 revolutions per minute.

4. The preparation method of the cyanosiloxane for high-voltage electrolytes according to claim 1, wherein, The purification treatment steps include a rotary evaporation step and a vacuum distillation step. Among them, vacuum distillation is carried out with gradient heating for rectification and purification.

5. The preparation method of the cyanosiloxane for high-voltage electrolytes according to claim 4, characterized in that, The gradient heating includes the following steps: The temperature of the rectification column is lower than 80°C, and the heating rate is controlled at 6°C / min; The temperature of the rectification column is 80°C - 100°C, and the heating rate is controlled at 2°C / min; The temperature of the rectification column is 100°C - 130°C, and the heating rate is controlled at 2°C / min; The temperature of the rectification column is higher than 130°C, and the heating rate is controlled at 2°C / min until distillate flows out.

6. The preparation method of the cyanosiloxane for high-voltage electrolytes according to claim 1, characterized in that, The molar ratio of reactant A to reactant B is (1.8 - 2.5):

1.

7. The preparation method of the cyanosiloxane for high-voltage electrolytes according to claim 1, characterized in that, The molar ratio of reactant A to the first organic solvent is 1:(1.5 - 3.5).

8. The preparation method of the cyanosiloxane for high-voltage electrolytes according to claim 1, characterized in that The molar ratio of reactant B to the second organic solvent is 1:(1.8 - 2.6).

9. A cyanosiloxane, characterized in that, It is prepared by the preparation method of the cyanosiloxane for high-voltage electrolytes described in any one of claims 1 - 8.

10. The cyanosiloxane according to claim 9, wherein, It has the following structural formula: Among them, both R1 and R2 are alkyl groups.

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