阅读说明：本技术 一种二氟磷酸锂的制备方法 (Preparation method of lithium difluorophosphate ) 是由 堀尾博英 于 2021-08-19 设计创作，主要内容包括：本申请公开了一种二氟磷酸锂的制备方法包括：在惰性气体条件下,将六氟磷酸锂溶解于非质子性溶剂,得到溶液A；在溶液A中,缓慢加入五氧化二磷和磷酸三锂,机械搅拌至混合均匀后得到溶液B；将溶液B在密闭条件下0-100℃,0-0.5Mpa机械搅拌反应2-8h；将步骤3中反应后的溶液进行固液分离,得到溶剂C,将溶剂C进行旋转蒸发至蒸干,得到产物D；取有机溶剂将产物D洗涤干燥后得到二氟磷酸锂。本申请的一种二氟磷酸锂的制备方法制得的二氟磷酸锂纯度在99.5％以上,且反应原料便宜易得,操作简单方便,简化了生产工艺同时节约了成本。(The application discloses a preparation method of lithium difluorophosphate, which comprises the following steps: dissolving lithium hexafluorophosphate in an aprotic solvent under the condition of inert gas to obtain a solution A; slowly adding phosphorus pentoxide and lithium phosphate into the solution A, and mechanically stirring until the phosphorus pentoxide and the lithium phosphate are uniformly mixed to obtain a solution B; the solution B is mechanically stirred and reacted for 2 to 8 hours under the closed condition at the temperature of between 0 and 100 ℃ and the pressure of between 0 and 0.5 Mpa; carrying out solid-liquid separation on the solution obtained after the reaction in the step 3 to obtain a solvent C, and carrying out rotary evaporation on the solvent C until the solvent C is evaporated to dryness to obtain a product D; and (4) taking an organic solvent to wash and dry the product D to obtain lithium difluorophosphate. The purity of the lithium difluorophosphate prepared by the preparation method of the lithium difluorophosphate is over 99.5 percent, the reaction raw materials are cheap and easy to obtain, the operation is simple and convenient, the production process is simplified, and the cost is saved.)

1. A preparation method of lithium difluorophosphate is characterized by comprising the following steps: the method comprises the following steps:

step 1: dissolving lithium hexafluorophosphate in an aprotic solvent under the condition of inert gas to obtain a solution A;

step 2: slowly adding phosphorus pentoxide and lithium phosphate into the solution A, and mechanically stirring until the phosphorus pentoxide and the lithium phosphate are uniformly mixed to obtain a solution B;

and step 3: under the closed condition, mechanically stirring the solution B, and reacting for 2-10 h;

and 4, step 4: carrying out solid-liquid separation on the solution obtained after the reaction in the step 3 to obtain a solvent C, and carrying out rotary evaporation on the solvent C until the solvent C is evaporated to dryness to obtain a product D;

and 5: and (4) taking an organic solvent to wash and dry the product D to obtain lithium difluorophosphate.

2. The method for preparing lithium difluorophosphate according to claim 1, wherein: the molar ratio of lithium hexafluorophosphate, lithium triphosphate and phosphorus pentoxide in the solution B is 2-5: 1-2.

3. The method for preparing lithium difluorophosphate according to claim 1, wherein: any one of diethyl carbonate, dimethyl carbonate and ethyl acetate is used as the aprotic solution.

4. The method for preparing lithium difluorophosphate according to claim 1, wherein: the organic solvent is any one of acetonitrile, diethyl ether, tetrahydrofuran, acetone and dioxane.

5. The method for preparing lithium difluorophosphate according to claim 1, wherein: the inert gas is any one of nitrogen, helium and argon.

6. The method for preparing lithium difluorophosphate according to claim 1, wherein: in the step 2, the reaction temperature is as follows: the reaction pressure is as follows at 0-100 ℃: 0-0.5Mpa, stirring parameters: 500-2000 r/min.

Technical Field

The application relates to the field of lithium battery synthesis, in particular to a preparation method of lithium difluorophosphate.

Background

With the increasing of electronic digital devices in the 21 st century, portable power supplies become indispensable products in the current society, and lithium batteries make outstanding contribution as novel mobile portable power supplies in the development of the technical field of microelectronics. The lithium battery plays a significant role in the aspects of 3c digital code, new energy automobiles and the like. With the support and affirmation of the state in policy, the lithium ion battery is vigorously developed in recent years to achieve the nobody's performance in the aspects of technology and products, and will be developed towards industrialization and specialization. Meanwhile, as the application field of lithium electrolyte is expanded, the performance requirement on the lithium battery is higher and higher. There are many problems in the development of lithium batteries, and lithium hexafluorophosphate, the most widely used electrolyte lithium salt, has not been satisfactory for use in the particular case of lithium batteries. The lithium difluorophosphate provided by the invention can form a more stable SEI film on the surface of a graphite cathode, so that the stability of the battery is improved, the cycle number is increased, the application range of high and low temperatures is wider, and the excellent performance on reducing the internal resistance of the battery is realized. Therefore, the lithium difluorophosphate has extremely high industrial value as a novel lithium battery electrolyte.

At present, the preparation method of lithium difluorophosphate is various. Such as: introducing phosphorus pentafluoride gas into hexamethyldisiloxane and dried methyl ethyl carbonate to prepare lithium difluorophosphate; or lithium hexafluorophosphate and misty tetramethoxysilane; lithium hexafluorophosphate is also produced with tris (trimethylsilyl) phosphite. The reaction is not easy to control, the conditions are complex, the number of byproducts is large, the raw materials are not easy to obtain, and the industrial development of lithium difluorophosphate is not facilitated.

Disclosure of Invention

The invention aims to provide a preparation method of lithium difluorophosphate, which overcomes the defects in the prior art.

In order to achieve the purpose, the invention provides the following technical scheme: a preparation method of lithium difluorophosphate comprises the following steps: step 1: dissolving lithium hexafluorophosphate in an aprotic solvent under the condition of inert gas to obtain a solution A;

step 2: slowly adding phosphorus pentoxide and lithium phosphate into the solution A, and mechanically stirring until the phosphorus pentoxide and the lithium phosphate are uniformly mixed to obtain a solution B;

and step 3: under the closed condition, mechanically stirring the solution B, and reacting for 2-10 h;

and 4, step 4: carrying out solid-liquid separation on the solution obtained after the reaction in the step 3 to obtain a solvent C, and carrying out rotary evaporation on the solvent C until the solvent C is evaporated to dryness to obtain a product D;

and 5: and (4) taking an organic solvent to wash and dry the product D to obtain lithium difluorophosphate.

In the technical scheme, the reaction equation of the invention is as follows:

Li₃PO₄+LiPF₆+P₂O₅→3LiPO₂F₂+LiPO₃；2LiPO₃+LiPF₆→3LiPO₂F₂。

preferably, the molar ratio of lithium hexafluorophosphate, lithium triphosphate and phosphorus pentoxide in the solution B in the step 2 is 2-5: 1-2.

Preferably, the aprotic solvent is any one of diethyl carbonate, dimethyl carbonate and ethyl acetate.

Preferably, the organic solvent is any one of acetonitrile, diethyl ether, tetrahydrofuran, acetone and dioxane.

Preferably, the inert gas is any one of nitrogen, helium and argon.

Preferably, in the step 2, the reaction temperature is: the reaction pressure is as follows at 0-100 ℃: 0-0.5Mpa, stirring parameters: 500-2000 r/min.

Compared with the prior art, the preparation method of lithium difluorophosphate has at least the following beneficial effects:

(1) lithium hexafluorophosphate, phosphorus pentoxide and lithium phosphate are adopted to react to prepare lithium difluorophosphate, an aprotic solvent is adopted as a reaction medium, the lithium difluorophosphate is reacted at a high temperature in a closed container, and then an organic solvent is used for purification to obtain the lithium difluorophosphate with higher purity.

(2) The purity of the lithium difluorophosphate prepared by the method is over 99.5 percent, and the lithium difluorophosphate can meet the requirement of serving as a lithium battery additive.

(3) The method has the advantages of cheap and easily-obtained reaction raw materials, simple and convenient operation, simplified production process and saved cost.

(4) The lithium difluorophosphate prepared by the method can improve the cycle performance and the high-temperature storage performance of the battery, and has a great industrial value.

Detailed Description

The technical solutions in the embodiments of the present invention will be described in detail below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Example 1

The preparation method of the lithium difluorophosphate comprises the following steps:

(1) under the protection of nitrogen, 1000ml of dimethyl carbonate is added into a closed container, then 2mol of lithium hexafluorophosphate, 1mol of lithium triphosphate and 1mol of phosphorus pentoxide are added, and the materials are mixed uniformly by mechanical stirring.

(2) Transferring the mixture obtained in the step (1) into a closed container, introducing nitrogen, pressurizing to 0.1Mpa, mechanically stirring at 25 ℃ and normal temperature for 1000r/min, and reacting for 2 hours.

(3) After the reaction is finished, cooling to room temperature, and carrying out vacuum filtration to separate solid from liquid of the reactant.

(4) And (4) carrying out rotary evaporation on the filtrate obtained in the step (3) at the temperature of 75 ℃, and removing dimethyl carbonate to obtain a solid crude product of lithium difluorophosphate.

(5) Washing the solid crude product obtained in the step (4) with 500ml of acetone, mechanically stirring for 1000r/min and 10min, and carrying out vacuum suction filtration to obtain filtrate.

(6) Rotary drying the filtrate obtained in the step (5) to obtain lithium difluorophosphate solid with the yield of 87.66 percent,

the purity was 99.5%.

Example 2

The preparation method of the lithium difluorophosphate comprises the following steps:

(1) under the protection of nitrogen, 1000ml of diethyl carbonate is added into a closed container, then 2.5mol of lithium hexafluorophosphate, 1.5mol of lithium triphosphate and 1mol of phosphorus pentoxide are added, and the materials are mixed uniformly by mechanical stirring.

(2) Transferring the mixture obtained in the step (1) into a closed container, introducing nitrogen, pressurizing to 0.1Mpa, heating to 50 ℃, mechanically stirring for 1000r/min, and reacting for 5 hours.

(3) After the reaction is finished, cooling to room temperature, and carrying out vacuum filtration to separate solid from liquid of the reactant.

(4) And (4) carrying out rotary evaporation on the filtrate obtained in the step (3) at the temperature of 75 ℃, and removing dimethyl carbonate to obtain a solid crude product of lithium difluorophosphate.

(5) Washing the solid crude product obtained in the step (4) with 500ml of diethyl ether, mechanically stirring for 1000r/min and 10min, and filtering under reduced pressure to obtain filtrate.

(6) And (5) carrying out rotary drying on the filtrate obtained in the step (5) to obtain a lithium difluorophosphate solid, wherein the yield is 94.56%, and the purity is 99.4%.

Example 3

The preparation method of the lithium difluorophosphate comprises the following steps:

(1) under the protection of nitrogen, 1000ml of ethyl acetate is added into a closed container, then 3mol of lithium hexafluorophosphate, 1.5mol of lithium triphosphate and 1.5mol of phosphorus pentoxide are added, and the materials are mixed uniformly by mechanical stirring.

(2) Transferring the mixture obtained in the step (1) into a closed container, introducing nitrogen, pressurizing to 0.2Mpa, heating to 60 ℃, mechanically stirring for 1500r/min, and reacting for 8 hours.

(3) After the reaction is finished, cooling to room temperature, and carrying out vacuum filtration to separate solid from liquid of the reactant.

(4) And (4) carrying out rotary evaporation on the filtrate obtained in the step (3) at the temperature of 75 ℃, and removing ethyl acetate to obtain a solid crude product of lithium difluorophosphate.

(5) Washing the solid crude product obtained in the step (4) with 500ml of diethyl ether, mechanically stirring for 1000r/min and 10min, and filtering under reduced pressure to obtain filtrate.

(6) And (5) carrying out rotary drying on the filtrate obtained in the step (5) to obtain a lithium difluorophosphate solid, wherein the yield is 90.34%, and the purity is 99.9%.

Example 4

The preparation method of the lithium difluorophosphate comprises the following steps:

(1) under the protection of nitrogen, 1000ml of dimethyl carbonate is added into a closed container, then 2.5mol of lithium hexafluorophosphate, 1mol of lithium triphosphate and 1.5mol of phosphorus pentoxide are added, and the materials are mixed uniformly by mechanical stirring.

(2) Transferring the mixture obtained in the step (1) into a closed container, introducing nitrogen, pressurizing to 0.1Mpa, heating to 80 ℃, mechanically stirring for 1500r/min, and reacting for 5 hours.

(3) After the reaction is finished, cooling to room temperature, and carrying out vacuum filtration to separate solid from liquid of the reactant.

(4) And (4) carrying out rotary evaporation on the filtrate obtained in the step (3) at the temperature of 75 ℃, and removing dimethyl carbonate to obtain a solid crude product of lithium difluorophosphate.

(5) Washing the solid crude product obtained in the step (4) with 500ml of acetonitrile, mechanically stirring for 1000r/min and 10min, and filtering under reduced pressure to obtain filtrate.

(6) Rotary drying the filtrate obtained in the step (5) to obtain lithium difluorophosphate solid with the yield of 89.12 percent,

the purity was 99.8%.

In summary, the method for preparing lithium difluorophosphate can prepare lithium difluorophosphate with the purity of more than 99.5%.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The foregoing is merely a detailed description of the present application, and it should be noted that modifications and embellishments could be made by those skilled in the art without departing from the principle of the present application, and these should also be considered as the protection scope of the present application.