A method for synthesizing lithium hexafluorophosphate

Abstract

The application discloses a kind of lithium hexafluorophosphate synthesis method, comprising the following steps: S1, LiF and AHF are added to pre-reaction kettle;S2, PCl5, AHF and Cl2 are added to PF5 reactor, and PF5 is prepared;S3, the product of S1 and S2 is added to main reaction kettle, and LiPF6 is prepared;S4, under the action of AHF and liquid nitrogen, LiPF6 prepared is crystallized in crystallization kettle, and LiPF6 crystal is obtained;Filtering is carried out through filter, and the mother liquor after filtering is introduced into pre-reaction kettle;LiPF6 crystal is precipitated and pressure filtration is carried out;S5, the LiPF6 in S4 is pre-dried, dried, cooled to obtain LiPF6.The application, raw material is widely, reaction process is easy to control, reaction time is short, production efficiency is high, product quality is stable and reliable, and high in purity.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium hexafluorophosphate synthesis, in particular to a lithium hexafluorophosphate synthesis method. BACKGROUND

[0002] Lithium hexafluorophosphate is a preferred electrolyte material in current lithium ion batteries, and has good ionic conductivity and electrochemical stability. At present, due to the multiple production links, complex process and high equipment requirement of lithium hexafluorophosphate preparation, the production cost of lithium hexafluorophosphate is high.

[0003] Publication No. CN1850592A discloses a method for preparing lithium hexafluorophosphate. The method comprises sublimation purification of phosphorus pentachloride, rectification purification of anhydrous hydrogen fluoride, reaction of the refined phosphorus pentachloride and the anhydrous hydrogen fluoride solution to obtain a mixed gas of phosphorus pentafluoride and hydrogen chloride, introduction of the mixed gas of phosphorus pentafluoride and hydrogen chloride into an anhydrous hydrogen fluoride solution of lithium fluoride, reaction, crystallization, separation and drying to obtain pure lithium hexafluorophosphate.

[0004] CN101353161A discloses a method for preparing phosphorus pentafluoride gas and lithium hexafluorophosphate by using the gas. In the method, phosphorus pentachloride is reacted with anhydrous hydrogen fluoride in the presence of an ether, acetonitrile, carbonate or ethyl acetate to prepare phosphorus pentafluoride. In addition, lithium fluoride is contacted with the phosphorus pentafluoride gas to prepare lithium hexafluorophosphate.

[0005] In summary, the prior art has complex preparation procedures, the reaction process is not easy to control, and the cost is high. Therefore, the application provides a lithium hexafluorophosphate synthesis method. SUMMARY

[0006] The application aims to provide a lithium hexafluorophosphate synthesis method to solve the problems in the prior art.

[0007] To achieve the above-mentioned purpose, the application provides the following technical scheme: a lithium hexafluorophosphate synthesis method, comprising the following steps:

[0008] S1, adding LiF and AHF into a pre-reaction kettle;

[0009] S2, adding PCl5, AHF and Cl2 into a PF5 reactor to prepare PF5;

[0010] S3, adding the products of S1 and S2 into a main reaction kettle to prepare LiPF6;

[0011] S4, under the action of AHF and liquid nitrogen, crystallizing the prepared LiPF6 in a crystallization kettle to obtain LiPF6 crystals; filtering through a filter, passing the filtered mother liquor into the pre-reaction kettle; and pressure filtering the precipitated LiPF6 crystals;

[0012] S5, pre-drying, drying and cooling the LiPF6 in S4 to obtain LiPF6.

[0013] Preferably, the preparation of AHF in S1 comprises the following steps:

[0014] S11, delivering anhydrous hydrofluoric acid into a buffer tank;

[0015] S12, delivering a certain amount of anhydrous hydrofluoric acid in the buffer tank into a feeding tank, and allowing the anhydrous hydrofluoric acid to flow through the buffer tower into a metering tank for metering by gravity;

[0016] S13, allowing the anhydrous hydrofluoric acid in the metering tank to flow through a primary filter and finally into a tower kettle;

[0017] S14, introducing hot water at 50-60℃ into the tower kettle, and obtaining high-purity anhydrous hydrofluoric acid gas by low-temperature evaporation;

[0018] S15, introducing the high-purity anhydrous hydrofluoric acid gas into a purification tower, and introducing a mixture of fluorine gas and nitrogen gas to react with the high-purity anhydrous hydrofluoric acid gas to obtain ultra-pure anhydrous hydrofluoric acid gas, which is obtained from the top of the purification tower;

[0019] S16, after the ultra-pure anhydrous hydrofluoric acid gas is condensed by a condenser, introducing it into a blending tank to adjust the required concentration.

[0020] Preferably, N2 is introduced in the pre-drying, drying and cooling in S5.

[0021] Preferably, the purity of the lithium hexafluorophosphate product prepared in S5 is above 99.98%.

[0022] Preferably, the gas generated in S5 is washed or electrostatically dedusted.

[0023] Compared with the prior art, the beneficial effects of the present application are as follows: under the action of AHF and liquid nitrogen, LiPF6 prepared is crystallized in a crystallization kettle to obtain LiPF6 crystals; the LiPF6 crystals are filtered by a filter, and the mother liquor after filtration is introduced into a pre-reaction kettle; the precipitated LiPF6 crystals are pressure-filtered; and the crystallized LiPF6 is pre-dried, dried and cooled to obtain LiPF6. 6； The raw materials are widely available, the reaction process is easy to control, the reaction time is short, the production efficiency is high, the product quality is stable and reliable, and the purity is high. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, which together with the embodiments of the present application serve to explain the present application, and do not constitute a limitation of the present application. In the drawings:

[0025] Figure 1 is a flow chart of the present application. DETAILED DESCRIPTION

[0026] For the purpose of making the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application.

[0027] Please refer to Figure 1 In the embodiments of the present application, a synthesis method of lithium hexafluorophosphate comprises the following steps:

[0028] S1, adding LiF and AHF into a pre-reaction kettle;

[0029] S2, adding PCl5, AHF and Cl2 into a PF5 reactor to prepare PF5;

[0030] S3, adding the products of S1 and S2 into a main reaction kettle to prepare LiPF6;

[0031] S4, under the action of AHF and liquid nitrogen, crystallizing the prepared LiPF6 in a crystallization kettle to obtain LiPF6 crystals; filtering through a filter, passing the filtered mother liquor into the pre-reaction kettle; and pressure filtering the precipitated LiPF6 crystals;

[0032] S5, pre-drying, drying and cooling the LiPF6 in S4 to obtain LiPF6.

[0033] Preferably, the preparation of AHF in S1 comprises the following steps:

[0034] S11, conveying anhydrous hydrofluoric acid into a buffer tank;

[0035] S12, conveying a certain amount of anhydrous hydrofluoric acid in the buffer tank into a feeding tank, and allowing the anhydrous hydrofluoric acid to flow through the buffer tower into a metering tank for metering under the action of gravity;

[0036] S13, allowing the anhydrous hydrofluoric acid in the metering tank to flow through a primary filter and finally into a tower kettle;

[0037] S14, passing hot water at 50-60℃ into the tower kettle to obtain high-purity anhydrous hydrofluoric acid gas by low-temperature evaporation;

[0038] S15, the high-purity anhydrous hydrofluoric acid gas is introduced into the purification tower, and a mixture of fluorine gas and nitrogen gas is introduced to react with the high-purity anhydrous hydrofluoric acid gas to obtain ultra-pure anhydrous hydrofluoric acid gas, which is obtained from the top of the purification tower;

[0039] S16, after the ultra-pure anhydrous hydrofluoric acid gas is condensed by the condenser, it is introduced into the adjusting tank to adjust the required concentration.

[0040] Preferably, the pre-drying, drying and cooling in S5 all need to introduce N2.

[0041] Preferably, the purity of the lithium hexafluorophosphate product prepared in S5 is above 99.98%.

[0042] Preferably, the gas generated in S5 is washed or electrostatically dedusted.

[0043] The working principle of the present application is that under the action of AHF and liquid nitrogen, the prepared LiPF6 is crystallized in the crystallization kettle to obtain LiPF6 crystals; the mother liquor after filtration is introduced into the pre-reaction kettle; the precipitated LiPF6 crystals are pressure filtered; the crystallized LiPF6 is pre-dried, dried and cooled to obtain LiPF6. 6； The raw materials are widely used, the reaction process is easy to control, the reaction time is short, the production efficiency is high, the product quality is stable and reliable, and the purity is high.

[0044] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for synthesizing lithium hexafluorophosphate, characterized in that, Includes the following steps: S1. Add LiF and AHF to the pre-reaction vessel; S2. PCl5, AHF and Cl2 are added to the PF5 reactor to prepare PF5; S3. Add the products of S1 and S2 into the main reactor to prepare LiPF6; S4. Under the action of AHF and liquid nitrogen, the prepared LiPF6 is crystallized in a crystallization kettle to obtain LiPF6 crystals; the crystals are then filtered through a filter, and the filtered mother liquor is passed into a pre-reaction kettle; the precipitated LiPF6 crystals are then pressure filtered. S5. Pre-dry, dry and cool the LiPF6 in S4 to obtain LiPF6; The preparation of AHF in S1 includes the following steps: S11. Transfer anhydrous hydrofluoric acid to the buffer tank; S12. A certain amount of anhydrous hydrofluoric acid in the buffer tank is transferred to the feeding tank. Under the action of gravity, the anhydrous hydrofluoric acid flows through the buffer tower and enters the metering tank for metering. S13. Allow the anhydrous hydrofluoric acid in the metering tank to flow through the primary filter and finally into the tower. S14. Introduce hot water at 50-60℃ into the column kettle and use low-temperature evaporation to obtain high-purity anhydrous hydrofluoric acid gas. S15. High-purity anhydrous hydrofluoric acid gas is introduced into the purification tower, and a mixture of fluorine and nitrogen is introduced to react with the high-purity anhydrous hydrofluoric acid gas to obtain ultrapure anhydrous hydrofluoric acid gas, which is obtained from the top of the purification tower. S16. Ultrapure anhydrous hydrofluoric acid gas is condensed by a condenser and then introduced into a mixing tank to adjust the required concentration.

2. The method for synthesizing lithium hexafluorophosphate according to claim 1, characterized in that, N2 needs to be introduced during the pre-drying, drying, and cooling processes in S5.

3. The method for synthesizing lithium hexafluorophosphate according to claim 1, characterized in that, The lithium hexafluorophosphate product prepared by S5 has a purity of over 99.98%.

4. The method for synthesizing lithium hexafluorophosphate according to claim 1, characterized in that, The gas generated in S5 is used for washing or electrostatic dust removal.

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