阅读说明：本技术 降低双氟磺酰亚胺锂盐中溶剂残留的方法 (Method for reducing solvent residue in lithium bis (fluorosulfonyl) imide ) 是由 吴国栋 沈鸣 李伟锋 袁青海 孔智梅 曹娜 于 2021-09-24 设计创作，主要内容包括：本发明涉及一种降低双氟磺酰亚胺锂盐中溶剂残留的方法,包括：(1)将第一良溶剂加入双氟磺酰亚胺锂盐和惰性溶剂的混合物中,经过滤后提供滤液；(2)将不同于第一良溶剂的第二良溶剂加入所述滤液中,形成混合溶液；(3)蒸发所述混合溶液,检测该混合溶液中第一良溶剂的残留比例是否小于1重量％；(4)若小于1重量％,则停止蒸发所述混合溶液,否则向混合溶液中加入所述惰性溶剂,并重复步骤(3),直至小于1重量％；和(5)过滤所述混合溶液,提供双氟磺酰亚胺锂盐成品。在本发明所述双氟磺酰亚胺锂盐成品中,残留的第一良溶剂≤100ppm,残留的第二良溶剂≤300ppm,以及残留的惰性溶剂≤300ppm。(The invention relates to a method for reducing solvent residue in lithium bis (fluorosulfonyl) imide, which comprises the following steps: (1) adding a first good solvent into a mixture of lithium bis (fluorosulfonyl) imide and an inert solvent, and filtering to obtain a filtrate; (2) adding a second good solvent different from the first good solvent into the filtrate to form a mixed solution; (3) evaporating the mixed solution, and detecting whether the residual proportion of the first good solvent in the mixed solution is less than 1 wt%; (4) if the weight percentage of the mixed solution is less than 1 percent, stopping evaporating the mixed solution, otherwise, adding the inert solvent into the mixed solution, and repeating the step (3) until the weight percentage of the mixed solution is less than 1 percent; and (5) filtering the mixed solution to provide a finished product of the lithium bis (fluorosulfonyl) imide. In the finished product of the lithium bis (fluorosulfonyl) imide salt, the residual first good solvent is less than or equal to 100ppm, the residual second good solvent is less than or equal to 300ppm, and the residual inert solvent is less than or equal to 300 ppm.)

1. A method of reducing solvent residue in lithium bis (fluorosulfonyl) imide, said method comprising:

adding a first good solvent into a mixture of lithium bis (fluorosulfonyl) imide and an inert solvent, and filtering to obtain a filtrate;

adding a second good solvent different from the first good solvent into the filtrate to form a mixed solution;

step (3), evaporating the mixed solution until the weight of the mixed solution is 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide, and detecting whether the residual proportion of the first good solvent in the mixed solution is less than 1 wt%;

step (4), if the residual proportion of the first good solvent in the mixed solution is less than 1 wt%, stopping evaporating the mixed solution, otherwise, adding the inert solvent into the mixed solution, and repeating the step (3) until the residual proportion of the first good solvent in the mixed solution is less than 1 wt%; and

and (5) filtering the mixed solution to provide a finished product of the lithium bis (fluorosulfonyl) imide.

2. The process of claim 1, wherein the inert solvent is selected from the group consisting of petroleum ether, toluene, xylene, n-hexane, cyclohexane, dichloromethane, chloroform, tetrachloroethane, 1, 1-dichloroethane, 1, 2-dichloroethane, 1, 1-dichloroethylene, 1, 2-dichloroethylene, 1,1, 1-trichloroethane, 1,1, 2-trichloroethane, 1,1,1, 2-tetrachloroethane, 1,1,2, 2-tetrachloroethane, 1, 1-dichloroethylene, 1, 2-dichloroethylene, 1,1, 1-trichloroethylene, 1,1, 2-trichloroethylene, 1,1,1, 2-tetrachloroethylene, 1,1,2, 2-tetrachloroethylene, and combinations of one or more of 1,1,2, 2-tetrachloroethylene.

3. The method of claim 1, wherein the first good solvent is selected from the group consisting of methyl ethyl ether, methyl vinyl ether, divinyl ether, methyl tert-butyl ether, diethyl ether, ethyl propyl ether, n-propyl vinyl ether, allyl vinyl ether, propyl ether, dipropenyl ether, methyl formate, ethyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, allyl acetate, n-butyl acetate, dimethyl carbonate, methyl ethyl carbonate, methyl vinyl carbonate, diethyl carbonate, acetonitrile, tetrahydrofuran, 1, 4-dioxane, and combinations thereof.

4. The method of claim 1, wherein the second good solvent is selected from one or more of methyl ethyl ether, methyl vinyl ether, divinyl ether, methyl tert-butyl ether, diethyl ether, ethyl propyl ether, n-propyl vinyl ether, allyl vinyl ether, propyl ether, dipropenyl ether, methyl formate, ethyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, allyl acetate, n-butyl acetate, dimethyl carbonate, methyl ethyl carbonate, methyl vinyl carbonate, diethyl carbonate, acetonitrile, propionitrile, butyronitrile, tetrahydrofuran, 2-methyltetrahydrofuran, and 1, 4-dioxane.

5. The method of claim 1, wherein the inert solvent is used in an amount ranging from 1 to 3 times the weight of the bis-fluorosulfonylimide salt; and the amount of the first good solvent is in the range of 1 to 3 times the weight of the bis-fluorosulfonyl imide salt.

6. The method of claim 1, wherein the second good solvent is present in an amount ranging from 3 wt% to 12 wt% based on the weight of the bis-fluorosulfonylimide salt.

7. The method of claim 1, wherein the step (1) comprises dissolving with stirring at any temperature between-5 ℃ and 15 ℃ after adding the first good solvent;

step (3) comprises evaporating the mixed solution at any temperature between 0 ℃ and 65 ℃ and under a vacuum degree of less than-0.095 MPa; and

and (5) filtering the mixed solution, and drying the filtered filter cake in vacuum at any temperature between 35 and 65 ℃ to obtain the finished product of the lithium bis (fluorosulfonyl) imide.

8. The method according to claim 1, wherein the inert solvent, the first good solvent and the second good solvent are added dropwise or at a time.

9. The method of claim 7, wherein step (5) comprises filtering the mixed solution, filtering the resulting filter cake with a nitrogen purge for 3 to 12 hours, vacuum drying the filter cake at room temperature for 6 to 24 hours, and further vacuum drying at an elevated temperature of 35 ℃ to 65 ℃ for 12 to 36 hours.

10. The method of claim 1, wherein the residual first good solvent is less than or equal to 100ppm, the residual second good solvent is less than or equal to 300ppm, and the residual inert solvent is less than or equal to 300ppm in the finished lithium bis (fluorosulfonyl) imide salt.

Technical Field

The invention relates to electrolyte salt for a power battery and an energy storage battery, in particular to a method for reducing solvent residue in lithium bis (fluorosulfonyl) imide.

Background

With the vigorous promotion of 'carbon peak reaching' and 'carbon neutralization' plans in China, a new energy industry chain can be developed vigorously, and the development of industries such as new energy automobiles, photovoltaic energy, wind power and other renewable energy storage industries is included. These industries have not been developed with high performance power or energy storage batteries. At present, the cost performance of the liquid ion battery is optimal, and the electrolyte salt related to the liquid ion battery is a key material for determining the excellent performance of the battery. Among the many electrolyte salts, the most comprehensive one is the bis-fluorosulfonyl imide salt. The lithium bis (fluorosulfonyl) imide salt is a novel electrolyte salt which is hopefully substituted for lithium hexafluorophosphate due to the characteristics of excellent high and low temperature performance, conductivity, low corrosivity and the like and can be applied to the formula of the power battery electrolyte on a large scale. The bifluorosulfonyl imide lithium salt serving as an electrolyte salt in a lithium ion battery electrolyte formula has high requirements on solvent residues in the preparation process of the bifluorosulfonyl imide lithium salt, and the electrolyte is polluted by trace solvent residues in the bifluorosulfonyl imide lithium salt, so that side effects such as damage to a solid electrolyte interface film (SEI) and the like are caused.

In the prior art, a conventional method for removing a solvent from lithium bifluoride sulfimide salt comprises the steps of dissolving the bifluoride sulfimide salt by using a benign solvent, evaporating the solvent under a reduced pressure condition to obtain a solid salt, and drying to obtain a finished product. The disadvantages of this conventional method are: in the process of evaporating solution crystallization, crystal particles are more or less wrapped by the used solvent in the purification process due to the growth speed of the crystal particles, so that the residual amount of the solvent is suddenly high or low, and the reproducibility is poor. And the residual solvent is wrapped in the crystal particles, so that the residual solvent is difficult to remove to the ppm level by conventional stirring and reduced pressure drying.

Therefore, there is a need for a novel method for reducing solvent residue in lithium bis (fluorosulfonyl) imide salt, so that the solvent residue in the final lithium bis (fluorosulfonyl) imide salt product with low solvent residue can reach ppm level.

Disclosure of Invention

It is an object of embodiments of the present invention to address the above and other deficiencies in the prior art. Aiming at the problems that solvent residue is difficult to remove and the like in the purification process of the conventional lithium bis (fluorosulfonyl) imide salt, the invention provides a method for reducing the solvent residue in the lithium bis (fluorosulfonyl) imide salt, which comprises the following steps:

(1) adding a first good solvent into a mixture of lithium bis (fluorosulfonyl) imide and an inert solvent, and filtering to obtain a filtrate;

(2) adding a second good solvent different from the first good solvent into the filtrate to form a mixed solution;

(3) evaporating the mixed solution until the weight of the mixed solution is 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide salt, and detecting whether the residual proportion of the first good solvent in the mixed solution is less than 1 wt%;

(4) if the residual proportion of the first good solvent in the mixed solution is less than 1 wt%, stopping evaporating the mixed solution, otherwise, adding the inert solvent into the mixed solution, and repeating the step (3) until the residual proportion of the first good solvent in the mixed solution is less than 1 wt%; and

(5) and filtering the mixed solution to provide a finished product of the lithium bis (fluorosulfonyl) imide.

In one embodiment of the invention, the inert solvent is selected from the group consisting of petroleum ether, toluene, xylene, n-hexane, cyclohexane, methylene chloride, chloroform, tetrachloroethane, 1, 1-dichloroethane, 1, 2-dichloroethane, 1, 1-dichloroethylene, 1, 2-dichloroethylene, 1,1, 1-trichloroethane, 1,1, 2-trichloroethane, 1,1,1, 2-tetrachloroethane, 1,1,2, 2-tetrachloroethane, 1, 1-dichloroethylene, 1, 2-dichloroethylene, 1,1, 1-trichloroethylene, 1,1, 2-trichloroethylene, 1,1,1, 2-tetrachloroethylene, 1,1,2, 2-tetrachloroethylene, and combinations of one or more thereof.

In one embodiment of the present invention, the first good solvent is selected from one or more of methyl ethyl ether, methyl vinyl ether, divinyl ether, methyl tert-butyl ether, diethyl ether, ethyl propyl ether, n-propyl vinyl ether, allyl vinyl ether, propyl ether, dipropenyl ether, methyl formate, ethyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, allyl acetate, n-butyl acetate, dimethyl carbonate, methyl ethyl carbonate, methyl vinyl carbonate, diethyl carbonate, acetonitrile, tetrahydrofuran, and 1, 4-dioxane.

In one embodiment of the present invention, the second good solvent is selected from one or more combinations of methyl ethyl ether, methyl vinyl ether, divinyl ether, methyl tert-butyl ether, diethyl ether, ethyl propyl ether, n-propyl vinyl ether, allyl vinyl ether, propyl ether, dipropenyl ether, methyl formate, ethyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, allyl acetate, n-butyl acetate, dimethyl carbonate, ethyl methyl carbonate, methyl vinyl carbonate, diethyl carbonate, acetonitrile, propionitrile, butyronitrile, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 4-dioxane.

In one embodiment of the present invention, the inert solvent and the first good solvent are used in an amount ranging from 1 to 3 times the weight of the bis-fluorosulfonyl imide salt.

In one embodiment of the present invention, the amount of the second good solvent ranges from 3 wt% to 12 wt% of the bis-fluorosulfonyl imide salt, based on the weight of the bis-fluorosulfonyl imide salt.

In one embodiment of the present invention, the step (1) comprises dissolving with stirring at any temperature between-5 ℃ and 15 ℃ after adding the first good solvent;

step (3) comprises evaporating the mixed solution at any temperature between 0 ℃ and 65 ℃ and under a vacuum degree of less than-0.095 MPa; and

and (5) filtering the mixed solution, and drying the filtered filter cake in vacuum at any temperature between 35 and 65 ℃ to obtain the finished product of the lithium bis (fluorosulfonyl) imide.

In one embodiment of the present invention, the inert solvent, the first good solvent, and the second good solvent are added dropwise or at once.

In one embodiment of the present invention, the step (5) comprises filtering the mixed solution, filtering the obtained filter cake with a nitrogen purge for 3 to 12 hours, vacuum-drying the filter cake at room temperature for 6 to 24 hours, and further vacuum-drying at elevated temperature of 35 ℃ to 65 ℃ for 12 to 36 hours.

In one embodiment of the invention, the residual first good solvent is less than or equal to 100ppm, the residual second good solvent is less than or equal to 300ppm, and the residual inert solvent is less than or equal to 300ppm in the finished lithium bis (fluorosulfonyl) imide salt.

Compared with the prior art, the method for reducing the solvent residue in the lithium bis (fluorosulfonyl) imide salt can reduce the solvent residue in a finished lithium bis (fluorosulfonyl) imide salt to the ppm level, for example, at least less than or equal to 300 ppm. Moreover, the method has good reproducibility, and the solvent residue in the prepared lithium bis (fluorosulfonyl) imide salt product is stable.

Detailed Description

The present invention will be described more fully hereinafter with reference to exemplary embodiments thereof. These exemplary embodiments are described so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

Furthermore, the technical features presented in the detailed description of the present application may be combined with each other to form a complete technical solution without conflict, and are within the scope of the present disclosure.

In the present invention, the term "good solvent" refers to a solvent having a strong dissolving power for a molecular solute (for example, lithium bis (fluorosulfonyl) imide), and in general, it is a solvent having an interaction parameter χ of less than 0.5 with the molecular solute.

In the present invention, the term "inert solvent" refers to a solvent which has no significant solubility for a molecular solute (e.g., lithium bis-fluorosulfonylimide), and generally is low in dielectric constant, non-polar, and does not undergo a proton autodelivery reaction nor solvation with the solute.

In the invention, the second good solvent as the hetero-solvent (fluxing agent) is used for changing the volatilization rates of different solvents in the crystallization process, so that the proportion of various solvents in the solution in the crystallization process is changed, and the solvent residue in the finished product of the lithium bis (fluorosulfonyl) imide is controlled to be in the ppm level. Preferably, the amount of the second good solvent as the hetero-solvent in the present invention is required to be smaller than that of the first good solvent, mainly for the purpose of controlling the solvent residue in the final product. If the amount of the second good solvent is too large, the solvent residue of the finished lithium bis (fluorosulfonyl) imide salt may be controlled to ppm, but the solvent residue of the first good solvent may be reduced, but the solvent residue of the second good solvent may be increased.

In the invention, the method for reducing the solvent residue in the lithium bis (fluorosulfonyl) imide salt comprises the steps of adding a first good solvent into a mixture of the lithium bis (fluorosulfonyl) imide salt and an inert solvent, and filtering to obtain a filtrate. In a specific embodiment of the present invention, the lithium bis (fluorosulfonyl) imide salt and the inert solvent are first mixed in an evaporation vessel with a stirring device, then the first good solvent is added into the evaporation vessel, and the lithium bis (fluorosulfonyl) imide salt is dissolved under stirring conditions of temperature reduction and/or heat preservation to form a solution containing the lithium bis (fluorosulfonyl) imide salt, the inert solvent and the first good solvent, and the solution is filtered to provide a filtrate.

In a specific embodiment of the invention, the inert solvent is a solvent which has no obvious dissolving capacity for lithium bis (fluorosulfonyl) imide, one or more combinations selected from the group consisting of petroleum ether, toluene, xylene, n-hexane, cyclohexane, dichloromethane, chloroform, tetrachloroethane, 1, 1-dichloroethane, 1, 2-dichloroethane, 1, 1-dichloroethylene, 1, 2-dichloroethylene, 1,1, 1-trichloroethane, 1,1, 2-trichloroethane, 1,1,1, 2-tetrachloroethane, 1,1,2, 2-tetrachloroethane, 1, 1-dichloroethylene, 1, 2-dichloroethylene, 1,1, 1-trichloroethylene, 1,1, 2-trichloroethylene, 1,1,1, 2-tetrachloroethylene, 1,1,2, 2-tetrachloroethylene.

In a specific embodiment of the present invention, the first good solvent is selected from one or more of methyl ethyl ether, methyl vinyl ether, divinyl ether, methyl tert-butyl ether, diethyl ether, ethyl propyl ether, n-propyl vinyl ether, allyl vinyl ether, propyl ether, dipropenyl ether, methyl formate, ethyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, allyl acetate, n-butyl acetate, dimethyl carbonate, methyl ethyl carbonate, methyl vinyl carbonate, diethyl carbonate, acetonitrile, tetrahydrofuran, and 1, 4-dioxane.

In the present invention, the evaporation vessel may be an evaporator which is conventional in the art, and the type thereof is not particularly limited as long as it can be used for evaporating various solvents used in the present invention. Typically, the evaporator comprises: (1) circulation type, in which the boiling solution passes the heating surface in a heating chamber for many times, such as central circulation tube type, suspension basket type, external heating type, lien type, forced circulation type, and the like; (2) single-pass type, in which the boiling solution passes through the heating surface in the heating chamber once without circulating flow, and the concentrated solution is discharged, such as rising film type, falling film type, stirring film type, centrifugal film type, etc.; and (3) direct contact type, in which a heating medium is in direct contact with the solution for heat transfer, such as a submerged combustion evaporator. In the operation process of the evaporation device, a large amount of heating steam is consumed, and in order to save the heating steam, a multi-effect evaporation device and a steam recompression evaporator can be adopted.

In a specific embodiment of the present invention, the inert solvent is used in an amount ranging from 1 to 3 times, from 1 to 2.5 times, from 1 to 2 times, from 1 to 1.5 times, from 1.5 to 3 times, from 1.5 to 2.5 times, from 1.5 to 2 times, from 2 to 3 times, from 2 to 2.5 times, or from 2.5 to 3 times the weight of the bis-fluorosulfonyl imide salt. The first good solvent is used in an amount ranging from 1 to 3 times, from 1 to 2.5 times, from 1 to 2 times, from 1 to 1.5 times, from 1.5 to 3 times, from 1.5 to 2.5 times, from 2 to 3 times, from 2 to 2.5 times, or from 2.5 to 3 times the weight of the bis-fluorosulfonyl imide salt.

In a specific embodiment of the present invention, the step (1) comprises stirring and dissolving at any temperature between-5 ℃ and 15 ℃, between-5 ℃ and 10 ℃, between-5 ℃ and 5 ℃, between-5 ℃ and 0 ℃, between 0 ℃ and 15 ℃, between 0 ℃ and 10 ℃, between 0 ℃ and 5 ℃, between 5 ℃ and 15 ℃, between 5 ℃ and 10 ℃ or between 10 ℃ and 15 ℃ after the first good solvent is added.

In the invention, the filtration is used for enabling the liquid in the solid-liquid suspension to permeate through the filter medium under the action of pushing force or other external force, and the solid particles and other substances are intercepted by the filter medium, so that the solid and other substances are separated from the liquid. Such filtration includes, but is not limited to, gravity filtration, pressure filtration and vacuum filtration, granular media filtration, cloth media filtration, porous ceramic media filtration, semi-permeable membrane media filtration, microporous filtration membranes. The filtration according to the invention can be a batch filter and/or a continuous filtration.

In the invention, the method for reducing the solvent residue in the lithium bis (fluorosulfonyl) imide salt comprises the step of adding a second good solvent into the filtrate to form a mixed solution. In a specific embodiment of the present invention, the second good solvent is selected from one or more combinations of methyl ethyl ether, methyl vinyl ether, divinyl ether, methyl tert-butyl ether, diethyl ether, ethyl propyl ether, n-propyl vinyl ether, allyl vinyl ether, propyl ether, dipropenyl ether, methyl formate, ethyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, allyl acetate, n-butyl acetate, dimethyl carbonate, ethyl methyl carbonate, methyl vinyl carbonate, diethyl carbonate, acetonitrile, propionitrile, butyronitrile, tetrahydrofuran, 2-methyltetrahydrofuran, and 1, 4-dioxane.

In a particular embodiment of the invention, the bis-fluorosulfonyl imide salt, the dosage range of the second good solvent is between 3 and 12 weight percent, 3 and 10 weight percent, 3 and 8 weight percent, 3 and 6 weight percent, 3 and 4 weight percent, 4 and 12 weight percent, 4 and 10 weight percent, 4 and 8 weight percent, 4 and 6 weight percent, 6 and 12 weight percent, 6 and 8 weight percent, 8 and 12 weight percent, 8 and 10 weight percent or 10 and 12 weight percent of the weight of the bis-fluorosulfonyl imide salt. In the present invention, if the amount of the second good solvent exceeds 12 wt% of the weight of the bis-fluorosulfonyl imide salt, the evaporation amount is easily increased, resulting in excessively high energy consumption; if the amount of the second good solvent is less than 3 wt% based on the weight of the bis-fluorosulfonyl imide salt, it is not enough to change the volatilization rate of the different solvents during crystallization.

In a specific embodiment of the present invention, the inert solvent, the first good solvent and/or the second good solvent are added dropwise or at a time. In the invention, the dropwise adding mode generates slow dissolving heat, which is beneficial to dissolving the bis (fluorosulfonyl) imide salt; the one-time adding mode can be matched with stirring and cooling so as to be beneficial to dissolving the bis-fluorosulfonyl imide salt.

In the present invention, the method for reducing the solvent residue in the lithium bis (fluorosulfonyl) imide salt includes evaporating a mixed solution including the lithium bis (fluorosulfonyl) imide salt, the inert solvent, the first good solvent, and the second good solvent until the weight of the mixed solution is 1 to 1.5 times, 1 to 1.4 times, 1 to 1.3 times, 1 to 1.2 times, 1 to 1.1 times, 1.1 to 1.5 times, 1.1 to 1.4 times, 1.1 to 1.3 times, 1.1 to 1.2 times, 1.2 to 1.5 times, 1.2 to 1.4 times, 1.2 to 1.3 times, 1.3 to 1.5 times, 1.3 to 1.4 times, 1.4 to 1.5 times, or 1 to 1.4 times of the weight of the lithium bis (fluorosulfonyl) imide salt, and detecting whether the residue ratio of the first good solvent in the mixed solution is less than 1 wt%, less than 0.8 wt%, less than 0.6 wt%, or less than 0.4 wt%.

In a specific embodiment of the invention, step (3) comprises a temperature range of between 0 ℃ and 65 ℃, between 0 ℃ and 55 ℃, between 0 ℃ and 45 ℃, between 0 ℃ and 35 ℃, between 0 ℃ and 25 ℃, between 0 ℃ and 15 ℃, between 0 ℃ and 5 ℃, between 5 ℃ and 65 ℃, between 5 ℃ and 55 ℃, between 5 ℃ and 45 ℃, between 5 ℃ and 35 ℃, between 5 ℃ and 25 ℃, between 5 ℃ and 15 ℃, between 15 ℃ and 65 ℃, between 15 ℃ and 55 ℃, between 15 ℃ and 45 ℃, between 15 ℃ and 35 ℃, between 15 ℃ and 25 ℃, between 25 ℃ and 65 ℃, between 25 ℃ and 55 ℃, between 25 ℃ and 45 ℃, between 25 ℃ and 35 ℃, between 35 ℃ and 65 ℃, between 35 ℃ and 55 ℃,), Evaporating the mixed solution at any temperature between 35 ℃ and 45 ℃, between 45 ℃ and 65 ℃, between 45 ℃ and 55 ℃, or between 55 ℃ and 65 ℃. In the present invention, the step (3) comprises evaporating the mixed solution under a vacuum degree of less than-0.095 MPa, less than-0.085 MPa, less than-0.075 MPa, less than-0.065 MPa, less than-0.055 MPa, less than-0.045 MPa, or less than-0.035 MPa.

In the present invention, the residual ratio of the first good solvent in the mixed solution can be detected by a conventional gas chromatography method. In a specific embodiment, the method for reducing solvent residue in lithium bis (fluorosulfonyl) imide comprises: if the residual proportion of the first good solvent in the mixed solution is less than 1 wt%, less than 0.8 wt%, less than 0.6 wt% or less than 0.4 wt%, the evaporation of the mixed solution is stopped, otherwise the inert solvent is added to the mixed solution, and step (3) is repeated until the residual proportion of the first good solvent in the mixed solution is less than 1 wt%, less than 0.8 wt%, less than 0.6 wt% or less than 0.4 wt%.

In the invention, the method for reducing the solvent residue in lithium bis (fluorosulfonyl) imide comprises the following steps: filtering the mixed solution remaining after evaporation, and drying the filter cake obtained by filtering in vacuum at any temperature of between 35 and 65 ℃, between 35 and 55 ℃, between 35 and 45 ℃, between 45 and 65 ℃, between 45 and 55 ℃ and between 55 and 65 ℃ to provide the finished product of the lithium bis (fluorosulfonyl) imide. In a specific embodiment, the method for reducing solvent residue in lithium bis (fluorosulfonyl) imide comprises: filtering the residual mixed solution after evaporation, blowing and filtering the obtained filter cake by nitrogen for 3-12 hours, 3-9 hours, 3-6 hours, 6-12 hours, 6-9 hours and 9-12 hours, drying the filter cake under the condition of room temperature for 6-24 hours, 6-20 hours, 6-16 hours, 6-12 hours, 12-24 hours, 12-20 hours, 12-16 hours, 16-24 hours, 16-20 hours or 20-24 hours in vacuum, then heating up to 35-65 ℃, 35-55 ℃, 35-45 ℃, 45-65 ℃, 45-55 ℃ and 55-65 ℃ for vacuum drying for 12-36 hours, 12-30 hours, 12-24 hours, 12-18 hours, 18-36 hours, 18-30 hours, 18-24 hours, 24-36 hours, 24-30 hours, or 30-36 hours.

In one embodiment of the present invention, the remaining first good solvent is less than or equal to 100ppm, less than or equal to 80ppm, or less than or equal to 60ppm, the remaining second good solvent is less than or equal to 300ppm, less than or equal to 250ppm, less than or equal to 200ppm, less than or equal to 150ppm, or less than or equal to 100ppm, and/or the remaining inert solvent is less than or equal to 300ppm, less than or equal to 250ppm, less than or equal to 200ppm, less than or equal to 150ppm, or less than or equal to 100ppm in the finished lithium bis (fluorosulfonyl) imide salt.

Specifically, the method for reducing the solvent residue in lithium bis (fluorosulfonyl) imide comprises the following steps:

mixing lithium bis (fluorosulfonyl) imide and an inert solvent in an evaporation container with stirring, and dropwise adding a first good solvent into the evaporation container; after the dropwise addition, stirring and dissolving the mixture under heat preservation, and then filtering the formed solution; after the filtration is finished, adding a second good solvent into the collected filtrate to form a mixed solution;

step two, concentrating and evaporating the mixed solution obtained in the step one at any temperature of between 0 and 65 ℃ and under a vacuum degree of less than-0.095 MPa to remove the solvent, and stopping concentrating and evaporating until the weight of the solution is 1 to 1.5 times of that of the lithium bis (fluorosulfonyl) imide salt and at any weight, taking the solution to detect whether the residual proportion of the first good solvent reaches the standard of less than 1 weight percent; if the solution reaches the standard, stopping evaporation, otherwise, continuously supplementing an inert solvent, concentrating and evaporating again to remove the solvent, stopping concentration and evaporation until the weight of the solution is 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide salt, then sampling and detecting, and repeating the operation in such a way until the residue of the first good solvent reaches the standard, and stopping concentration to form a concentrated solution; and

and step three, filtering the concentrated solution obtained in the step two, purging the obtained filter cake with nitrogen, and then drying in vacuum to finally obtain the finished product of the low-solvent-residue lithium bis (fluorosulfonyl) imide.

Examples

The present invention will be described in further detail with reference to specific examples, so that the advantages of the present invention will be more apparent. It should be understood that the description is intended for purposes of illustration only and is not intended to limit the scope of the present disclosure. The experimental procedures, in which specific conditions are not specified, in the following examples are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers.

Example 1

First, 500 g of lithium bis (fluorosulfonyl) imide salt and 750 g of 1,1, 2-trichloroethane were mixed in an evaporation vessel equipped with a stirrer, and after cooling to 15 ℃, 750 g of methyl acetate was added dropwise to the evaporation vessel. After the dropwise addition, the solution was dissolved by stirring while maintaining the temperature, and then the solution was filtered through a microporous membrane. After the filtration was completed, 50 g of 1, 4-dioxane was added to the collected filtrate to form a mixed solution.

Secondly, the mixed solution is concentrated and evaporated in a water bath with the pressure of less than-0.095 MPa and the temperature of 45 ℃ until the concentration is stopped when the weight of the solution is any weight 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide. At this time, the solution was examined whether the residual ratio of methyl acetate was < 1% by weight. And if the weight percent of the solution is less than 1 percent, stopping evaporation, otherwise, continuously adding 1,1, 2-trichloroethane, concentrating, evaporating and desolventizing again, stopping concentration when the weight of the solution is 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide salt, sampling and detecting, and repeating the operation until the residual proportion of the methyl acetate is less than 1 percent by weight, and stopping concentration and evaporation to form a concentrated solution.

And finally, filtering the concentrated solution, purging the obtained filter cake for 6 hours by using nitrogen, then carrying out vacuum drying for 9 hours at room temperature, and continuing to heat to 55 ℃ for vacuum drying for 15 hours. 450 g of finished product of the lithium bis (fluorosulfonyl) imide is finally obtained, and the residual value of methyl acetate is 6ppm, the residual value of 1, 4-dioxane is 2ppm, and the residual value of 1,1, 2-trichloroethane is 50ppm through conventional gas chromatography detection.

Example 2

First, 500 g of lithium bis (fluorosulfonyl) imide salt and 750 g of 1, 2-dichloroethane were mixed in an evaporation vessel equipped with a stirrer, and after cooling to 5 ℃, 750 g of diethyl ether was added dropwise to the evaporation vessel. After the dropwise addition, the solution was dissolved by stirring while maintaining the temperature, and then the solution was filtered through a microporous membrane. After the completion of filtration, 25 g of acetonitrile was added to the collected filtrate to form a mixed solution.

Secondly, the mixed solution is concentrated and evaporated in a water bath with the pressure of less than-0.095 MPa and the temperature of 30 ℃ until the concentration is stopped when the weight of the solution is any weight 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide. At this time, the solution was examined whether the residual ratio of ether was < 1% by weight. And if the weight percent of the solution is less than 1 percent, stopping evaporation, otherwise, continuously adding 1, 2-dichloroethane, concentrating, evaporating and desolventizing again, stopping concentration when the weight of the solution is 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide salt, sampling, detecting, and repeating the operation until the residual proportion of the diethyl ether is less than 1 percent by weight, and stopping concentration and evaporation to form a concentrated solution.

And finally, filtering the concentrated solution, blowing the obtained filter cake for 3 hours by using nitrogen, then carrying out vacuum drying for 6 hours at room temperature, and then continuously heating to 40 ℃ and carrying out vacuum drying for 12 hours. 451 g of finished product of the lithium bis (fluorosulfonyl) imide is finally obtained. The residue of diethyl ether was 6ppm, the residue of acetonitrile was 2ppm and the residue of 1, 2-dichloroethane was 150ppm, as determined by conventional gas chromatography.

Example 3

First, 500 g of lithium bis (fluorosulfonyl) imide salt and 750 g of 1,1,2, 2-tetrachloroethylene were mixed in an evaporation vessel equipped with a stirrer, and after cooling to 10 ℃, 750 g of acetonitrile was added dropwise to the evaporation vessel. After the dropwise addition, the solution was dissolved by stirring while maintaining the temperature, and then the solution was filtered through a microporous membrane. After the filtration was completed, 60 g of dimethyl carbonate was added to the collected filtrate to form a mixed solution.

Secondly, the mixed solution is concentrated and evaporated in a water bath with the pressure of less than-0.095 MPa and the temperature of 65 ℃ until the concentration is stopped when the weight of the solution is any weight 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide. At this time, the solution was examined for the presence or absence of acetonitrile residue ratio of < 1% by weight. And if the weight percent of the acetonitrile is less than 1 percent, stopping evaporation, otherwise, continuously adding 1,1,2, 2-tetrachloroethylene, concentrating, evaporating and desolventizing again, stopping concentration when the weight of the solution is 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide salt, sampling, detecting, and repeating the operation until the residual proportion of the acetonitrile is less than 1 percent by weight, and stopping concentration and evaporation to form a concentrated solution.

And finally, filtering the concentrated solution, purging the obtained filter cake for 9 hours by using nitrogen, then carrying out vacuum drying for 20 hours at room temperature, and continuing to heat to 65 ℃ for vacuum drying for 30 hours. 452 g of finished product of lithium bis (fluorosulfonyl) imide is finally obtained. The residue of acetonitrile was 36ppm, the residue of dimethyl carbonate was 22ppm and the residue of 1,1,2, 2-tetrachloroethylene was 200ppm, as determined by conventional gas chromatography.

Comparative example 1

Firstly, 500 g of lithium bis (fluorosulfonyl) imide salt and 750 g of methyl acetate are mixed, stirred and dissolved at a constant temperature, and then the solution is filtered through a microporous filter membrane, and the filtrate is collected.

Secondly, the filtrate is concentrated and evaporated in a water bath at 45 ℃ under vacuum at a pressure of < -0.095MPa until the whole solution is extracted without solvent and becomes a solid salt.

Thirdly, dichloromethane was added to the solid salt, which was then filtered, and the resulting filter cake was purged with nitrogen for 9 hours, then vacuum dried at room temperature for 20 hours, and then further vacuum dried at elevated temperature to 65 ℃ for 30 hours. Finally obtaining the lithium bis (fluorosulfonyl) imide, wherein the residual value of methyl acetate is 800ppm, and the residual value of dichloromethane is 1070 ppm.

Comparative example 2

Firstly, 500 g of lithium bis (fluorosulfonyl) imide salt and 750 g of 1, 2-dichloroethane are mixed in an evaporation container with a stirrer, after the temperature is reduced to 5 ℃, 750 g of diethyl ether is dropwise added into the evaporation container, after the dropwise addition is finished, the solution is stirred and dissolved under heat preservation, then the solution is filtered by a microporous filter membrane, and after the filtration is finished, the filtrate is collected.

Secondly, the mixed solution is concentrated and evaporated in a water bath with the pressure of less than-0.095 MPa and the temperature of 30 ℃, and the concentration is stopped until the weight of the solution is any weight between 1 and 1.5 times of that of the lithium bis (fluorosulfonyl) imide. At this time, the solution was examined whether the residual ratio of ether was < 1% by weight. And if the weight percent of the solution is less than 1 percent, stopping evaporation, otherwise, continuously adding 1, 2-dichloroethane, concentrating, evaporating and desolventizing again, stopping concentration when the weight of the solution is 1-1.5 times of that of the lithium bis (fluorosulfonyl) imide salt, sampling, detecting, and repeating the operation until the ether residue is less than 1 percent by weight, and stopping concentration and evaporation to form a concentrated solution.

And finally, filtering the obtained concentrated solution, purging the obtained filter cake for 3 hours by using nitrogen, then carrying out vacuum drying for 6 hours at room temperature, and then continuously heating to 40 ℃ and carrying out vacuum drying for 12 hours. 451 g of lithium bis (fluorosulfonyl) imide salt was finally obtained, wherein the residue of diethyl ether was 996ppm and the residue of 1, 2-dichloroethane was 817 ppm.

Comparative example 3

Firstly, 500 g of lithium bis (fluorosulfonyl) imide salt and 750 g of acetonitrile are mixed and dissolved at room temperature with stirring, and then the solution is filtered through a microporous filter membrane, and the filtrate is collected after the filtration is finished.

Secondly, the obtained filtrate is concentrated, evaporated and desolventized in a water bath with the temperature of 65 ℃ under the vacuum condition that the pressure is less than-0.095 MPa, until most of the salt is separated out, the concentration and evaporation are stopped, and a concentrated solution is formed.

Finally, 1000 g of n-hexane was added to the concentrated solution, followed by filtration, and the obtained filter cake was vacuum-dried at 65 ℃ for 30 hours with stirring. 452 g of lithium bis (fluorosulfonyl) imide salt was finally obtained, wherein the residue of acetonitrile was 1136ppm, and the residue of n-hexane was 1132 ppm.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.