阅读说明：本技术 二氟磷酸锂的合成工艺及合成装置 (Synthesis process and synthesis device of lithium difluorophosphate ) 是由 陈建生 王天桃 于 2021-02-08 设计创作，主要内容包括：本发明提供一种二氟磷酸锂的合成工艺及合成装置,属于二氟磷酸锂合成技术领域,合成工艺在于,以磷氧化合物、氟化锂、五氟化磷为原料,在无水氟化氢介质中,反应生成二氟磷酸锂；具体在惰性气体保护下,先将磷氧化合物、氟化锂加入到无水氟化氢介质中,然后通入五氟化磷反应。本发明以磷氧化合物、氟化锂、五氟化磷为原料,在无水氟化氢介质中,一步合成二氟磷酸锂,工艺流程短,生产成本低,相较于采用六氟磷酸锂为原料,本发明的生产成本要低50％以上；本发明的工艺不会生成水,且不含氯离子,产品质量高。(The invention provides a synthesis process and a synthesis device of lithium difluorophosphate, belonging to the technical field of lithium difluorophosphate synthesis, wherein the synthesis process comprises the steps of taking a phosphorus oxide compound, lithium fluoride and phosphorus pentafluoride as raw materials, and reacting in an anhydrous hydrogen fluoride medium to generate the lithium difluorophosphate; specifically, under the protection of inert gas, a phosphorus-oxygen compound and lithium fluoride are added into an anhydrous hydrogen fluoride medium, and then phosphorus pentafluoride is introduced for reaction. The method takes phosphorus oxide, lithium fluoride and phosphorus pentafluoride as raw materials, and synthesizes the lithium difluorophosphate in one step in an anhydrous hydrogen fluoride medium, so that the process flow is short, the production cost is low, and compared with the method which adopts lithium hexafluorophosphate as a raw material, the method has the advantage that the production cost is reduced by more than 50%; the process of the invention does not generate water, does not contain chloride ions and has high product quality.)

1. The synthesis process of lithium difluorophosphate is characterized in that a phosphorus oxide, lithium fluoride and phosphorus pentafluoride are used as raw materials and react in an anhydrous hydrogen fluoride medium to generate the lithium difluorophosphate.

2. The process for synthesizing lithium difluorophosphate as claimed in claim 1, wherein under the protection of inert gas, the phosphorus-oxygen compound and lithium fluoride are added into the anhydrous hydrogen fluoride medium, and then phosphorus pentafluoride is introduced for reaction.

3. The process for synthesizing lithium difluorophosphate as claimed in claim 2, wherein the addition temperature of the phosphorus-oxygen compound and the lithium fluoride is controlled to be-10-10 ℃.

4. The synthesis process of lithium difluorophosphate according to claim 2, wherein the reaction temperature is controlled to be 0-15 ℃ and the reaction time is 1-8 h.

5. The process for synthesizing lithium difluorophosphate as claimed in claim 1, wherein the phosphorus-oxygen compound is one selected from polyphosphoric acid, metaphosphoric acid and phosphoric anhydride.

6. The process for synthesizing lithium difluorophosphate according to claim 1, wherein the reaction product of a phosphorus-oxygen compound, lithium fluoride and phosphorus pentafluoride is filtered and then subjected to an evaporation treatment to remove hydrogen fluoride, thereby obtaining a solid amount; and condensing and recovering the evaporated hydrogen fluoride.

7. The process for synthesizing lithium difluorophosphate as claimed in claim 6, wherein the solid content is dissolved, crystallized, separated and dried to obtain lithium difluorophosphate.

8. Lithium difluorophosphate's synthesizer characterized in that includes:

the reaction unit is used for reacting phosphorus oxide, lithium fluoride and phosphorus pentafluoride;

a filtering unit for filtering the reaction product generated by the reaction unit to remove insoluble substances;

the evaporation crystallization unit is used for evaporating out hydrogen fluoride in the reaction product and crystallizing the product after removing the hydrogen fluoride to obtain a crystallized material;

and the drying unit is used for drying the crystallized materials under the protection of inert gas.

9. The synthesis device of lithium difluorophosphate as claimed in claim 8, wherein the reaction unit consists of an A reaction kettle and a B reaction kettle which are communicated with each other, and the A reaction kettle and the B reaction kettle alternately serve as main reaction kettles to carry out reaction so that phosphorus pentafluoride is completely absorbed.

10. The apparatus for synthesizing lithium difluorophosphate of claim 8, further comprising:

and the condensation recovery unit is communicated with the evaporation crystallization unit and is used for recovering the hydrogen fluoride from the evaporation part.

Technical Field

The invention belongs to the technical field of synthesis of lithium difluorophosphate, and particularly relates to a synthesis process of lithium difluorophosphate.

Background

In recent years, lithium difluorophosphate (LiPO)₂F₂) The functional additive with excellent performance is widely applied to the electrolyte of a lithium ion secondary battery to overcome the defects that the most common lithium salt used in the current commercial lithium ion battery, namely lithium hexafluorophosphate (LiPF6), has poor chemical stability and is extremely sensitive to water and heat. LiPO₂F₂Can form low-impedance interfacial films on the surfaces of the anode and the cathode of the lithium ion battery,side reactions between the electrode and the electrolyte are suppressed, thereby improving the cycle life of the battery.

With LiPO₂F₂The preparation research of the compound is also more and more concerned. Current LiPO₂F₂The preparation method can be divided into three methods according to the raw material routes, namely a difluorophosphoric acid method, a lithium hexafluorophosphate method and other methods.

In the earlier literature, LiPO was prepared by reacting Li, O, LiOH with difluorophosphoric anhydride₂F₂The method has water generated during the preparation process, so that the prepared LiPO₂F₂There is a possibility of hydrolysis. Japanese Dajin company patent (JP2014132932) discloses the preparation of difluorophosphoric acid by reacting phosphorus oxyhalides, phosphorus oxyacids (anhydrides) and hydrogen fluoride, followed by reaction with LiOH, Li₂CO₃Preparation of LiPO by neutralization reaction₂F₂It is stated in the patent that LiPO is preferred in the neutralization process₂F₂The high-purity product can be obtained by controlling the excessive alkali of the non-aqueous good solvent, and the yield is high; however, the experimental data show that the water content and acidity are high. In Chinese patent (CN201510639734.9), after the alcoholysis of metaphosphoric acid, the fluorination of hydrogen fluoride is carried out to obtain monofluorophosphoric acid, the reaction of monofluorophosphoric acid and phosphorus trifluoride gas is carried out to obtain difluorophosphoric acid, and then the difluorophosphoric acid reacts with lithium chloride, and the whole preparation process generates no water, thereby avoiding the generation of LiPO₂F₂Hydrolysis, but the use of chloride salts as lithium sources may introduce chloride ion impurities. Another chinese patent (CN200780031231.7) uses lithium hexafluorophosphate and organosiloxane containing Si-O-Si structure to prepare electrolyte containing difluorophosphate, the fluorinated silane obtained after reaction has low boiling point, is easy to remove, has extremely high selectivity, and data shows no other impurities are introduced, but the cost is relatively high because lithium hexafluorophosphate is used as raw material.

Disclosure of Invention

Based on the background problem, the invention aims to provide a synthesis process of lithium difluorophosphate, which has the advantages of low cost, no water and no chloride ions, and high purity of the prepared lithium difluorophosphate; the invention also aims to provide a synthesis device of lithium difluorophosphate.

In order to achieve the above object, on one hand, the embodiment of the present invention provides a technical solution:

a synthesis process of lithium difluorophosphate takes a phosphorus oxide, lithium fluoride and phosphorus pentafluoride as raw materials, and lithium difluorophosphate is generated by reaction in an anhydrous hydrogen fluoride medium.

Preferably, under the protection of inert gas, the phosphorus-oxygen compound and the lithium fluoride are firstly added into an anhydrous hydrogen fluoride medium, and then phosphorus pentafluoride is introduced for reaction.

In one embodiment, the addition temperature of the phosphorus-oxygen compound and the lithium fluoride is controlled to be-10-10 ℃.

In one embodiment, the reaction temperature is controlled to be 0-15 ℃ and the reaction time is 1-8 h.

In one embodiment, the phosphorus-oxygen compound is selected from one of polyphosphoric acid, metaphosphoric acid, phosphoric anhydride.

In one embodiment, after filtering the reaction product of the phosphorus-oxygen compound, lithium fluoride and phosphorus pentafluoride, evaporating to remove hydrogen fluoride to obtain solid; and condensing and recovering the evaporated hydrogen fluoride.

Preferably, the solid content is dissolved, crystallized, separated and dried to obtain the lithium difluorophosphate.

On the other hand, the embodiment of the present invention further provides a lithium difluorophosphate synthesis apparatus, including:

the reaction unit is used for reacting phosphorus oxide, lithium fluoride and phosphorus pentafluoride;

a filtering unit for filtering the reaction product generated by the reaction unit to remove insoluble substances;

the evaporation crystallization unit is used for evaporating out hydrogen fluoride in the reaction product and crystallizing the product after removing the hydrogen fluoride to obtain a crystallized material;

and the drying unit is used for drying the crystallized materials under the protection of inert gas.

In one embodiment, the reaction unit consists of an A reaction kettle and a B reaction kettle which are communicated with each other, and the A reaction kettle and the B reaction kettle alternately serve as main reaction kettles to react so that phosphorus pentafluoride is completely absorbed.

In one embodiment, the apparatus for synthesizing lithium difluorophosphate further comprises:

and the condensation recovery unit is communicated with the evaporation crystallization unit and is used for recovering the hydrogen fluoride from the evaporation part.

Compared with the prior art, the invention has the following effects:

1. the method takes phosphorus oxide, lithium fluoride and phosphorus pentafluoride as raw materials, and synthesizes the lithium difluorophosphate in an anhydrous hydrogen fluoride medium by one step, so that the process flow is short, the production cost is low, and compared with the method which adopts lithium hexafluorophosphate as a raw material (1 ton of lithium difluorophosphate is produced by 1.5 tons of lithium hexafluorophosphate), the production cost is reduced by more than 50%; the process of the invention does not contain chloride ions and has high product quality.

2. The raw materials are added under the protection of inert gas, so that moisture in the air can be isolated, namely, water cannot be generated by the process.

3. The invention controls the adding temperature of phosphorus oxide and lithium fluoride to be-10-10 ℃, and controls the reaction temperature to be 0-15 ℃ so as to prevent the anhydrous hydrogen fluoride from gasifying.

4. The phosphorus oxide and the lithium fluoride are added into the anhydrous hydrogen fluoride medium, and then the phosphorus pentafluoride gas is introduced for reaction, so that the control of the reaction end point is facilitated, and the yield is controllable.

5. The synthesis process has high yield which can reach 92-95%, and the product purity is more than or equal to 99.5%; the utilization rate of the raw materials is high, the vaporized hydrogen fluoride can be recycled, and byproducts are not generated; the reaction temperature of the invention is lower than 100 ℃, the reaction pressure is normal pressure, and the reaction condition is mild and safe.

6. The reaction unit of the synthesis device is formed by the A reaction kettle and the B reaction kettle which are communicated, the A reaction kettle and the B reaction kettle alternately work as a main reaction kettle, and unabsorbed phosphorus pentafluoride gas in the main reaction kettle can enter another auxiliary reaction kettle to continue to react, so that the utilization rate of the phosphorus pentafluoride gas is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below.

FIG. 1 is a schematic view of a lithium difluorophosphate synthesizing apparatus in example 1 of the present invention;

fig. 2 is a schematic flow chart of a lithium difluorophosphate synthesis process in embodiment 3 of the present invention.

Detailed Description

The invention provides a synthesis process of lithium difluorophosphate, which takes phosphorus oxide, lithium fluoride and phosphorus pentafluoride as raw materials, and synthesizes the lithium difluorophosphate in one step in an anhydrous hydrogen fluoride medium, and has short process flow and low production cost; in addition, the process of the invention does not generate water, does not contain chloride ions and has high product quality.

The invention will be elucidated by means of specific embodiments.

Example 1

The lithium difluorophosphate synthesis apparatus, as shown in fig. 1, includes: the device comprises a reaction unit, a filtering unit, an evaporation and crystallization unit, a drying unit and a recovery unit.

In the embodiment, the reaction unit is used for the reaction of phosphorus-oxygen compound, lithium fluoride and phosphorus pentafluoride; specifically, the reaction unit consists of an A reaction kettle 1 and a B reaction kettle 2, and the A reaction kettle 1 and the B reaction kettle 2 are alternately used as main reaction kettles to carry out reaction.

When A reaction kettle 1 is used as a main reaction kettle, B reaction kettle 2 is used as an auxiliary reaction kettle, anhydrous hydrogen fluoride, phosphorus oxide compound and lithium fluoride are added into A reaction kettle 1, anhydrous hydrogen fluoride, phosphorus oxide compound and lithium fluoride are also added into B reaction kettle 2, and then the anhydrous hydrogen fluoride, phosphorus oxide compound and lithium fluoride are added into A reaction kettle1Phosphorus pentafluoride gas is introduced into the reaction kettle A, the reaction is finished after the phosphorus pentafluoride gas is absorbed and saturated in the reaction kettle A1, the unabsorbed phosphorus pentafluoride gas enters the reaction kettle B2 to continue the reaction, and at the moment, the reaction product in the reaction kettle A1 enters the filtering unit.

Then taking the B reaction kettle 2 as a main reaction kettle and the A reaction kettle 1 as an auxiliary reaction kettle, putting the next batch of raw materials into the A reaction kettle 1, and introducing phosphorus pentafluoride gas into the B reaction kettle 2 for reaction until the phosphorus pentafluoride gas in the B reaction kettle 2 is absorbed and saturated, and reactingThe phosphorus pentafluoride gas which is not absorbed enters the A reaction kettle1Continuously reacting; thereby realize A reation kettle 1 and B reation kettle 2's alternation and go on as main reation kettle, guarantee that the phosphorus pentafluoride gas is not wasted, increase of utilization ratio.

In the embodiment, the filtering unit is used for filtering the reaction product generated by the reaction unit to remove insoluble substances; specifically, the filter unit is a filter 3, the filter is made of PTFE, the pore size of the filter is 1 to 0.2 μm, the filter 3 is an existing product, and the structure of the filter is not described in detail in this embodiment.

In this embodiment, the evaporation crystallization unit is configured to evaporate hydrogen fluoride from the reaction product, and crystallize the product after removing hydrogen fluoride to obtain a crystallized material; specifically, the evaporative crystallization unit comprises an evaporative crystallization kettle 4, and the filtered reaction product enters the evaporative crystallization kettle 4 to evaporate the hydrogen fluoride solvent and obtain a solid amount; the evaporation crystallization kettle 4 is communicated with the recovery unit, the recovery unit is a condensation recoverer 5, the evaporated hydrogen fluoride enters the condensation recoverer 5 for condensation and recovery, and the recovered hydrogen fluoride can be reused.

Crystallizing the solid in an evaporation crystallization kettle 4 to obtain a crystallized material, separating the crystallized material in a centrifuge 6, and recovering a centrifugal mother liquor as a solvent; and after separation, the lithium difluorophosphate enters the drying unit under the protection of inert gas, in the embodiment, the drying unit is a dryer 7, and the lithium difluorophosphate product is obtained after drying by the dryer 7.

The overflowing parts of the reaction kettle A1, the reaction kettle B2, the filter 3 and the evaporation crystallization kettle 4 are made of anhydrous hydrogen fluoride resistant materials such as Hastelloy, polytetrafluoroethylene, polyvinylidene fluoride and the like.

Example 2

Different from the synthesis device of lithium difluorophosphate in the embodiment 1, the reaction unit of the embodiment only comprises one reaction kettle.

Example 3

The synthesis process of lithium difluorophosphate adopts the synthesis device in embodiment 1, and the synthesis process is shown in fig. 2, and specifically comprises the following steps:

(1) replacing the reaction kettle A1 and the reaction kettle B2 with high-purity nitrogen for three times, then adding 1000mL of hydrogen fluoride into the reaction kettle A1 and the reaction kettle B2 respectively, and starting a stirrer;

(2) under the protection of nitrogen, adding 65g of lithium fluoride and 295g of phosphorus pentoxide into the A reaction kettle 1 in three times, adding 65g of lithium fluoride and 295g of phosphorus pentoxide into the B reaction kettle 2 in three times, controlling the temperature of the A reaction kettle 1 and the B reaction kettle 2 to be minus 8 +/-2 ℃, and controlling the pressure of nitrogen to be 0.1-0.5 MPa;

(3) after stirring for 1h, introducing phosphorus pentafluoride gas into the reaction kettle A1, controlling the reaction temperature to be 2 +/-2 ℃, and reacting for 8h to obtain a reaction product, wherein the phosphorus pentafluoride gas is not absorbed in the reaction kettle A1 any more, the reaction is finished, and the unabsorbed phosphorus pentafluoride gas enters the reaction kettle B2 for continuous reaction;

the reaction equation is shown as the following formula:

5LiF+PF₅+2P₂O₅＝＝5LiPO₂F₂

(4) introducing the reaction product obtained in the reaction kettle 1 in the step (3) into a filter 3 for filtering, introducing the filtered reaction product into an evaporation crystallization kettle 4, heating to 45-50 ℃, evaporating out a hydrogen fluoride solvent, and entering a condensation recoverer 5 for recovery to obtain a solid after evaporation is finished;

(5) adding 900mL of DMC solvent into the evaporative crystallization kettle 4, stirring until the solid content is completely dissolved and the solution is transparent, then reducing the temperature of the evaporative crystallization kettle 4 to 5 ℃, crystallizing for 2 hours under stirring, then carrying out centrifugal filtration to obtain a crystallization material, and recycling centrifugal mother liquor;

(6) the crystallized material was fed into a drier 6 and dried with a stream of 70 ℃ dry nitrogen for 4.5 hours to obtain 507.6g of white crystals, 94% yield and 99.7% product purity.

Example 4

The synthesis process of lithium difluorophosphate by using the synthesis device in the embodiment 1 comprises the following steps:

(1) replacing the reaction kettle A1 and the reaction kettle B2 with high-purity nitrogen for three times, then adding 1000mL of hydrogen fluoride into the reaction kettle A1 and the reaction kettle B2 respectively, and starting a stirrer;

(2) under the protection of nitrogen, adding 65g of lithium fluoride and 295g of phosphorus pentoxide into the A reaction kettle 1 in three times, adding 65g of lithium fluoride and 295g of phosphorus pentoxide into the B reaction kettle 2 in three times, controlling the temperature of the A reaction kettle 1 and the B reaction kettle 2 to be 8 +/-2 ℃, and controlling the pressure of nitrogen to be 0.1-0.5 MPa;

(3) after stirring for 1h, introducing phosphorus pentafluoride gas into the reaction kettle A1, controlling the reaction temperature to be 8 +/-2 ℃, and reacting for 2h to obtain a reaction product, wherein the phosphorus pentafluoride gas is not absorbed in the reaction kettle A1 any more, the reaction is finished, and the unabsorbed phosphorus pentafluoride gas enters the reaction kettle B2 for continuous reaction;

the reaction equation is shown as the following formula:

5LiF+PF₅+2P₂O₅＝＝5LiPO₂F₂

(4) introducing the reaction product obtained in the step (3) into a filter 3 for filtering, introducing the filtered reaction product into an evaporation crystallization kettle 4, heating to 45-50 ℃, evaporating out a hydrogen fluoride solvent, and introducing the hydrogen fluoride solvent into a condensation recoverer 5 for recovery to obtain a solid amount after evaporation is finished;

(5) adding 900mL of DMC solvent into the evaporative crystallization kettle 4, stirring until the solid content is completely dissolved and the solution is transparent, then reducing the temperature of the evaporative crystallization kettle 4 to 0 ℃, crystallizing for 5 hours under stirring, then centrifugally filtering to obtain a crystallization material, and recycling centrifugal mother liquor;

(6) the crystallized material was fed into a drier 6 and dried with a stream of 70 ℃ dry nitrogen for 4.5 hours to obtain 502.2g of white crystals, 93% yield and 99.6% product purity.

Example 5

The synthesis process of lithium difluorophosphate by using the synthesis device in the embodiment 1 comprises the following steps:

(1) replacing the reaction kettle A1 and the reaction kettle B2 with high-purity nitrogen for three times, then adding 1000mL of hydrogen fluoride into the reaction kettle A1 and the reaction kettle B2 respectively, and starting a stirrer;

(2) under the protection of nitrogen, adding 65g of lithium fluoride and 295g of phosphorus pentoxide into the A reaction kettle 1 in three times, adding 65g of lithium fluoride and 295g of phosphorus pentoxide into the B reaction kettle 2 in three times, controlling the temperature of the A reaction kettle 1 and the B reaction kettle 2 to be minus 3 +/-2 ℃, and controlling the pressure of nitrogen to be 0.1-0.5 MPa;

(3) after stirring for 1h, introducing phosphorus pentafluoride gas into the reaction kettle A1, controlling the reaction temperature to be 13 +/-2 ℃, reacting for 5h to obtain a reaction product, wherein the phosphorus pentafluoride gas is not absorbed in the reaction kettle A1 any more, the reaction is finished, and the unabsorbed phosphorus pentafluoride gas enters the reaction kettle B2 for continuous reaction;

the reaction equation is shown as the following formula:

5LiF+PF₅+2P₂O₅＝＝5LiPO₂F₂

(4) introducing the reaction product obtained in the step (3) into a filter 3 for filtering, introducing the filtered reaction product into an evaporation crystallization kettle 4, heating to 45-50 ℃, evaporating out a hydrogen fluoride solvent, and introducing the hydrogen fluoride solvent into a condensation recoverer 5 for recovery to obtain a solid amount after evaporation is finished;

(5) adding 900mL of DMC solvent into the evaporative crystallization kettle 4, stirring until the solid content is completely dissolved and the solution is transparent, then reducing the temperature of the evaporative crystallization kettle 4 to-10 ℃, crystallizing for 9 hours under stirring, then carrying out centrifugal filtration to obtain a crystallization material, and recycling centrifugal mother liquor;

(6) the crystallized material was fed into a drier 6 and dried with a stream of 70 ℃ dry nitrogen for 4.5 hours to give 513g of white crystals with a yield of 95% and a product purity of 99.7%.

Example 6

The synthesis process of lithium difluorophosphate is different from that of example 5 in that the phosphorus-oxygen compound in this example is polyphosphoric acid, the addition amount of polyphosphoric acid is 300g, and the rest of the reaction process is the same as that of example 5, and the reaction equation is as follows:

5LiF+PF₅+2H₆P₄O₁₃＝＝5LiPO₂F₂+4H₃PO₄

502g of white crystals are finally obtained, the yield is 93%, and the product purity is 99.5%.

Example 7

The synthesis process of lithium difluorophosphate is different from that of example 5 in that the phosphorus-oxygen compound in this example is metaphosphoric acid, the addition amount of metaphosphoric acid is 300g, and the rest of the reaction process is the same as that of example 5, and the reaction equation is:

5LiF+PF₅+6HPO₃＝＝5LiPO₂F₂+2H₃PO₄

497g of white crystal is finally obtained, the yield is 92%, and the product purity is 99.5%.

It should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept of the present invention, and these changes and modifications belong to the protection scope of the present invention.