阅读说明：本技术 利用电化学合成双氟磺酸亚胺锂的方法 (Method for electrochemically synthesizing lithium bis (fluorosulfonate) imide ) 是由 靳军 于 2019-11-07 设计创作，主要内容包括：本发明公开了一种利用电化学合成双氟磺酸亚胺锂的方法,其制备方法为：将电解池的温度调节至0-18℃,以两个镍板分别作为阳极和阴极,在电解池中加入适量无水氢氟酸进行电解；待电解池内的电流稳定后,往电解池内加入适量的双氯磺酸亚胺,待双氯磺酸亚胺溶解后,调节电解池的工作电压至5-8V；待电流降到5mA以下时,取出电解池内的溶液；将电解池内取出的溶液常压蒸馏,使双氟磺酸亚胺与无水氢氟酸分离,冷却后得到高纯度的无色液体的双氟磺酸亚胺。然后,用氢氧化锂与其反应,过滤后,重结晶得到高纯的双氟磺酸亚胺锂。本发明由于采用了电化学预除水和氯离子,同时用电化学来氟化没有引入金属卤化物为催化剂,因此本发明工艺简单,耗能少,成本低,且其制备的LiFSI的纯度高。(The invention discloses a method for electrochemically synthesizing lithium bis (fluorosulfonate) imide, which comprises the following steps: adjusting the temperature of the electrolytic cell to 0-18 ℃, taking two nickel plates as an anode and a cathode respectively, and adding a proper amount of anhydrous hydrofluoric acid into the electrolytic cell for electrolysis; after the current in the electrolytic cell is stable, adding a proper amount of dichlorosulfoimide into the electrolytic cell, and after the dichlorosulfoimide is dissolved, adjusting the working voltage of the electrolytic cell to 5-8V; when the current is reduced to below 5mA, taking out the solution in the electrolytic cell; and distilling the solution taken out of the electrolytic cell at normal pressure to separate the difluoride imine from the anhydrous hydrofluoric acid, and cooling to obtain the high-purity colorless liquid difluoride imine. Then, lithium hydroxide is used for reaction, and after filtration and recrystallization, high-purity lithium bis (fluorosulfonate) imide is obtained. The invention adopts electrochemistry to pre-remove water and chloride ions, and uses electrochemistry to fluorinate without introducing metal halide as catalyst, so the invention has simple process, low energy consumption, low cost and high purity of the prepared LiFSI.)

1. A method for electrochemically synthesizing lithium bis (fluorosulfonate) imide, which is characterized by comprising the following steps: it comprises the following steps:

step one, synthesizing dichlorosulfonic acid imine: under magnetic stirring, adding 100-110g ammonium chloride into a round-bottom flask containing 300-350g thionyl chloride and 450-500g chlorosulfonic acid, heating to raise the temperature of the mixed solution to 70-100 ℃ for reaction to generate sulfur dioxide and hydrogen chloride gas, taking out the sulfur dioxide and the hydrogen chloride gas by using nitrogen, and absorbing the hydrogen chloride gas by using a sodium hydroxide aqueous solution; distilling after reacting for 30-40h, collecting the fraction at the temperature of 115-120 ℃, and cooling to obtain 185-200g of colorless dichloroimine liquid, wherein the yield of the dichloroimine is 86.9-93.6%;

step two, reducing the water content of the anhydrous hydrofluoric acid: adjusting the temperature of a polytetrafluoroethylene electrolytic cell to 0-18 ℃, taking two nickel plates as an anode and a cathode respectively, adding a proper amount of anhydrous hydrofluoric acid into the electrolytic cell, adjusting the working voltage of a direct current power supply in the electrolytic cell to 1.6-5V, and monitoring the current value in the electrolytic cell in real time by using a current meter;

step three, synthesizing the bis-fluorosulfonic acid imine: after the current in the electrolytic cell is stable, adding the bischlorosulfoacid imine prepared in the first step into the electrolytic cell, wherein the volume ratio of the added bischlorosulfoacid imine to the anhydrous hydrofluoric acid is 1: 30-40, after the dichlorosulfoimide is dissolved, adjusting the working voltage of the electrolytic cell to 5-8V; when the current is reduced to be below 5mA, the power supply experiment is closed and stopped; taking out the solution in the electrolytic cell;

step four, purifying the bis (fluorosulfonic acid) imine liquid: putting the solution taken out of the electrolytic cell into a distiller, distilling at normal pressure to separate the difluoride imine from the anhydrous hydrofluoric acid, and cooling to obtain high-purity colorless difluoride imine liquid;

step five, synthesizing lithium bis (fluorosulfonate) imide: keeping the temperature at 0-10 ℃ under the stirring of a magnetic stirrer, mixing 10-15g of the bis (fluorosulfonic acid) imine liquid prepared in the step four with 130-140g of dichloromethane and 10-15g of thionyl chloride solution in a round-bottom flask, adding 1.3-1.7g of anhydrous lithium hydroxide into the mixed solution, stirring for 30min, heating the solution to 20-30 ℃, and continuing to react for 2 h; then heating the liquid to 50 ℃, distilling and concentrating to separate out lithium difluoride sulfonate imine, and filtering to obtain a filter cake;

step six, preparing the lithium bis (fluorosulfonate) imide crystal: and C, adding 40-55g of dichloromethane, 40-55g of ethanol and 0.15-0.3g of ethylene diamine tetraacetic acid tetrasodium solution into the filter cake prepared in the step five, pulping, filtering and drying to obtain 8-15g of lithium bis (fluorosulfonate) imide crystal, wherein the product yield is 92.8-95.1%.

2. The method for electrochemically synthesizing lithium bis (fluorosulfonate) imide according to claim 1, wherein: the purification method of the lithium bis (fluorosulfonate) imide prepared in the sixth step comprises the following steps: under magnetic stirring, adding 9-10g of lithium bis (fluorosulfonate) imide into 100mL of a mixed solution of dichloromethane and ethanol, wherein the volume ratio of dichloromethane to ethanol is 1:1, recrystallizing, heating the mixed solution to 55-65 ℃, cooling the solution to room temperature after lithium bis (fluorosulfonate) imide is completely dissolved, cooling to 0 ℃, standing for 30min, and filtering the precipitated solid to obtain 9-9.9g of white lithium bis (fluorosulfonate) imide crystals.

3. The method for electrochemically synthesizing lithium bis (fluorosulfonate) imide according to claim 1 or 2, wherein: in the first step, a coolant circulating pipeline is arranged on the outer side of the electrolytic cell, and the temperature of the electrolytic cell is kept between 0 and 18 ℃ through coolant circulation.

4. The method for electrochemically synthesizing lithium bis (fluorosulfonate) imide according to claim 3, wherein: the rotating speed of the magnetic stirring in the first step and the fifth step is 1000-1500 r/min.

Technical Field

The invention relates to the technical field of chemical reagent preparation, in particular to a method for electrochemically synthesizing lithium bis (fluorosulfonate) imide.

Background

Lithium batteries are gradually and widely applied as novel green energy equipment, key materials of the lithium ion batteries comprise an anode, a cathode, a binder, a diaphragm and electrolyte, wherein the electrolyte plays a role in charge transmission between the anode and the cathode in the batteries, and is a key composition of the lithium ion batteries, the electrolyte obviously influences the cycle and service life, safety performance and energy of the batteries, and the lithium bis-fluorosulfonyl imide (LiFSI) is a novel electrolyte lithium salt used in the lithium battery electrolyte, is environment-friendly and has good safety performance. The purity and the cost of the bis (fluorosulfonyl) imide (HFSI) which is used as a raw material for synthesizing the bis (fluorosulfonyl) imide Lithium (LiFSI) are important for the battery performance and whether the industrial production of the bis (fluorosulfonyl) imide Lithium (LiFSI) can be realized.

Chinese patent CN104671224 discloses a method for synthesizing bis-fluorosulfonyl imide salt, which utilizes at least two of antimony fluoride, potassium fluoride, zinc fluoride and aluminum fluoride to form a compound fluoride salt, so that bis-fluorosulfonyl imide salt is subjected to effective fluorination reaction in an organic solvent; after the reaction is finished, filtering the reaction solution, and concentrating; and crystallizing, filtering and drying the concentrated solution to obtain the high-purity bis (fluorosulfonyl) imide salt, thereby further improving the fluorination efficiency. Chinese patent CN103935970A discloses a method for preparing bis (fluorosulfonyl) imide and its alkali metal salts, wherein hydrogen fluoride is used as a fluorinating agent and a reaction solvent to react with HClSI and alkali metal halide to prepare the alkali metal salts of bis (fluorosulfonyl) imide, and the hydrogen fluoride is relatively easy to obtain and has low raw material cost, thereby reducing the production cost; the reaction product is the bis-fluorosulfonyl imide and the hydrogen chloride, and other complex reaction byproducts do not exist, so that the material consumption and the waste generation are reduced, and the utilization rate of raw materials, the product yield and the purity are improved. Anhydrous hydrogen fluoride is also used as the fluorinating agent, but in order to further improve the fluorination conversion rate, SbCl is used in the reaction process₅、TiCl₄、SnCl₄The amount ratio of the bischlorosulfonimide to the catalyst is preferably 1 (0.05-1).

In the synthesis method, fluorine or chlorinated metal salt is used as a catalyst for fluorination of the bis (fluorosulfonic acid) imide (hclSI), other heteroatoms are introduced into a reaction system, and the purity of the synthesized bis (fluorosulfonic acid) imide (HFSI) is difficult to reach the battery-grade standard and cannot be directly applied to large-scale industrialization.

Disclosure of Invention

The invention aims to provide a method for electrochemically synthesizing lithium bis (fluorosulfonate) imide, which avoids the use of highly toxic metal halides as catalysts, reduces heteroatoms, improves the purity of products, and reduces synthesis cost.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for synthesizing lithium bis (fluorosulfonate) imide by utilizing electrochemistry comprises the following steps:

step one, synthesizing dichlorosulfonic acid imine: under magnetic stirring, 300-350g thionyl chloride (SOCl) was added₂) And 450-₃H) 100-110g ammonium chloride (NH) was added to the round bottom flask₄Cl), heating to raise the temperature of the mixed solution to 70-100 ℃ for reaction to generate SO₂And HCl gas, taken out with nitrogen, absorbed with aqueous sodium hydroxide (NaOH); distilling after reacting for 30-40h, collecting the fraction at the temperature of 115-120 ℃, and cooling to obtain 185-200g of colorless dichlorosulfoimide (HCSI) liquid, wherein the yield of the dichlorosulfoimide is 86.9-93.6%; the chemical reaction that takes place in step one is shown in (1).

Step two, reducing the water content of the anhydrous hydrofluoric acid: adjusting the temperature of a polytetrafluoroethylene electrolytic cell to 0-18 ℃, taking two nickel plates as an anode and a cathode respectively, adding a proper amount of anhydrous hydrofluoric acid into the electrolytic cell, adjusting the working voltage of a direct current power supply of the electrolytic cell to 1.6-5V, and monitoring the current value in the electrolytic cell in real time by using a current meter. The chemical reaction in the second step is shown as (2);

step three, synthesizing the bis-fluorosulfonic acid imine: after the current in the electrolytic cell is stable, adding the bischlorosulfoacid imine prepared in the first step into the electrolytic cell, wherein the volume ratio of the added bischlorosulfoacid imine to the anhydrous hydrofluoric acid is 1: 30-40, after the dichlorosulfoimide is dissolved, adjusting the working voltage of the electrolytic cell to 5-8V; when the current is reduced to be below 5mA, the power supply experiment is closed and stopped; and taking out the solution in the electrolytic cell. The chemical reaction generated in the third step is shown as (3); HCl is also removed at the same time and a chemical reaction takes place as shown in (4).

Step four, purifying the bis (fluorosulfonic acid) imine liquid: putting the solution taken out of the electrolytic cell into a distiller, distilling at normal pressure to separate the difluoride imine from the anhydrous hydrofluoric acid, and cooling to obtain high-purity colorless difluoride imine liquid;

step five, synthesizing lithium bis (fluorosulfonate) imide: under the stirring of a magnetic cable, keeping the temperature at 0-10 ℃, mixing 10-15g of the difluoride sulfonic acid imine liquid prepared in the step four with 130-; then heating the liquid to 80-100 ℃, distilling and concentrating to separate out lithium difluoride sulfonate imine, and filtering to obtain a filter cake; the chemical reaction in the fifth step is shown as (5);

step six, preparing the lithium bis (fluorosulfonate) imide crystal: adding 40-55g of dichloromethane, 40-55g of ethanol and 0.15-0.3g of ethylene diamine tetraacetic acid tetrasodium solution into the filter cake prepared in the fifth step, pulping, filtering and drying to obtain 8-15g of lithium bis (fluorosulfonate) imide crystal, wherein the product yield is 92.8-95.1%;

preferably, the method for purifying lithium bis (fluorosulfonate) imide prepared in the sixth step comprises the following steps: under magnetic stirring, adding 9-10g of lithium bis (fluorosulfonate) imide into 100mL of dichloromethane and ethanol, mixing in a round-bottom flask, wherein the volume ratio of dichloromethane to ethanol is 1:1, recrystallizing, heating the mixed solution to 55-65 ℃, cooling the solution to room temperature after lithium bis (fluorosulfonate) imide is completely dissolved, cooling to 0 ℃, standing for 30min, and filtering the precipitated solid to obtain 9-9.9g of white lithium bis (fluorosulfonate) imide crystals (LiFSI).

Preferably, in the first step, a coolant circulation pipe is installed at the outer side of the electrolytic cell, and the temperature of the electrolytic cell is maintained at 0-18 ℃ by the coolant circulation.

Preferably, the rotation speed of the magnetic stirring in the first step and the fifth step is 1000-.

According to the invention, water and chloride ions are removed in advance by electrochemistry, metal halide is not introduced as a catalyst for fluorination by electrochemistry, lithium hydroxide is used for reacting with lithium bifluorosulfonate imide salt, and after filtration, recrystallization is carried out to obtain battery-grade lithium bifluorosulfonate imide.

In the first step of the method, sulfur dioxide and hydrogen chloride gas are generated while the dichlorosulfoimide is generated, are taken out by using nitrogen and are absorbed by a sodium hydroxide aqueous solution, and byproducts are removed. The chemical reaction formula is as follows:

and step two, the water content of the raw material, namely the anhydrous hydrofluoric acid, before the reaction is further reduced through the electrolysis operation of the electrolytic cell.

The chemical reaction formula of the bis (fluorosulfonic acid) imine generated by the reaction in the third step is shown as the formula (3), and hydrogen chloride generated by the reaction is electrolyzed into hydrogen and chlorine at the same time.

And fifthly, generating the lithium bis (fluorosulfonate) imide salt according to the formula (5).

The invention has the beneficial effects that:

the electrochemical method is adopted to remove water in advance and further remove chloride ions and some cations, and the electrochemical method is used to fluorinate the bis (chloro) sulfonic acid imine (HClSI) at the same time, so that a fluorinating reagent is avoided, thereby avoiding the introduction of other ions and finally obtaining the battery-grade bis (fluoro) sulfonic acid imine Lithium (LiFSI) crystal. Therefore, the method has the advantages of simple process, low energy consumption and low cost, and the prepared lithium bis (fluorosulfonate) imide (LiFSI) has high purity.

Detailed Description

The present invention will be described in further detail with reference to examples.