A continuous production system of lithium hexafluorophosphate

Abstract

The application belongs to the technical field of lithium hexafluorophosphate production, and particularly relates to a lithium hexafluorophosphate continuous production system. The system comprises a phosphorus pentafluoride preparation part and a lithium hexafluorophosphate preparation part. The phosphorus pentafluoride preparation part comprises a PF5 generating device, a water removal device, a POF3 condensing device and a phosphoric acid dehydration device. The lithium hexafluorophosphate preparation part comprises a reaction device, a crystallization device, a separation device, a drying device and a LiF dissolving device. The system can continuously and smoothly operate, and feeding and discharging can be carried out without shutdown, so that the production efficiency is greatly improved. The PF5 generating device, the water removal device and the phosphoric acid dehydration device are mutually cooperative, so that not only anhydrous phosphorus pentafluoride can be efficiently and low-cost prepared, but also phosphorus resources can be cyclically and comprehensively utilized.

Description

Technical Field

[0001] This invention belongs to the field of lithium hexafluorophosphate production technology, specifically relating to a continuous production system for lithium hexafluorophosphate. Background Technology

[0002] Lithium hexafluorophosphate (LiPF6) is one of the core materials for lithium-ion batteries, and its quality determines the charge-discharge performance, lifespan, and safety of lithium-ion batteries. Due to its advantages such as excellent ionic conductivity, long cycle life, high specific energy, low self-discharge, no memory effect, and simple and environmentally friendly waste disposal, it has become the preferred electrolyte for commercial lithium-ion batteries. With the huge market demand and promising development prospects of the new energy vehicle and lithium-ion battery industries, the market demand for LiPF6 will grow in tandem, resulting in exceptionally broad prospects for industrial development.

[0003] The basic method for producing lithium hexafluorophosphate currently involves dissolving lithium fluoride in an anhydrous hydrogen fluoride solution to form a lithium fluoride hydrogen fluoride solution. The anhydrous hydrogen fluoride then reacts with phosphorus pentoxide to produce phosphorus pentafluoride. This phosphorus pentafluoride gas is then introduced into the aforementioned lithium fluoride hydrogen fluoride solution. Following reaction, crystallization, separation, and drying, a pure lithium hexafluorophosphate product is obtained. It is generally necessary to remove impurities from the phosphorus pentafluoride before it enters the reaction system; otherwise, the product quality will be reduced.

[0004] CN114604833A provides a method for preparing phosphorus pentafluoride, comprising the following steps: 1) adding phosphorus pentoxide to anhydrous hydrogen fluoride, and after the addition of phosphorus pentoxide is complete, adding sulfur trioxide to the reaction system, heating the reaction to obtain a mixed gas containing phosphorus pentafluoride; 2) condensing the mixed gas containing phosphorus pentafluoride to obtain the phosphorus pentafluoride. The preparation process uses sulfur trioxide, which leads to the subsequent generation of a large amount of fluorinated sulfuric acid, making it difficult to handle.

[0005] Patents CN219829182U and CN217780758U use a multi-stage condensation system and a distillation device to purify phosphorus pentafluoride, respectively. The equipment is complex, has high energy consumption, and high maintenance costs. Utility Model Content

[0006] To overcome the above shortcomings, this application provides a continuous lithium hexafluorophosphate production system, including a phosphorus pentafluoride preparation unit and a lithium hexafluorophosphate preparation unit. The phosphorus pentafluoride preparation unit uses phosphorus pentoxide (P2O5) to react with hydrogen fluoride to prepare phosphorus pentafluoride. It does not use sulfur trioxide and does not produce fluorine-containing sulfuric acid. The reaction products are only a small amount of water vapor, HF and phosphorus trifluoride oxychloride (POF3) impurities. Through the ingenious design of the internal structure of the components and the synergistic effect between the components, the phosphorus pentafluoride is thoroughly cleaned of impurities.

[0007] Specifically, a continuous production system for lithium hexafluorophosphate includes a phosphorus pentafluoride preparation unit and a lithium hexafluorophosphate preparation unit. The phosphorus pentafluoride preparation unit includes a PF5 generator, a dehydration unit, a POF3 condensation unit, and a phosphoric acid dehydration unit. Both the PF5 generator and the dehydration unit are provided with a long and narrow reaction chamber. An overflow-type sloping reaction platform is provided inside the chamber. The reaction platform is used to support solid reaction raw materials. The air inlet and the exhaust outlet are respectively located at both ends of the long and narrow reaction chamber.

[0008] Furthermore, the inclined reaction platform has an angle of 15-45° with the horizontal plane, and the platform is treated with anti-slip material to prevent solid reactants from sliding under weight. The anti-slip treatment includes, but is not limited to, etching, sandblasting, and the addition of baffles.

[0009] The POF3 condensation device is a low-temperature condensation device. PF5 gas containing POF3 impurities is cooled to below the boiling point of POF3, and the POF3 impurities condense into liquid or solid and remain in the device, while PF5 flows out in gaseous form.

[0010] The phosphoric acid dehydration device is a tunnel type, with a liquid inlet and a solid outlet located at both ends of the tunnel. A movable sagger is installed inside the tunnel to carry the material.

[0011] The lithium hexafluorophosphate preparation unit includes a reaction device, a crystallization device, a separation device, a drying device, and a LiF dissolution device. The reaction device is equipped with a stirring paddle, and the crystallization device is equipped with multiple parallel S-shaped pipes, with an ultrasonic generator around the pipes.

[0012] When the above-mentioned phosphorus pentafluoride preparation unit is working, solid P2O5 is placed on the inclined reaction platform of the PF5 generator. Hydrogen fluoride gas is introduced through the gas inlet. Under the condition of 150-250℃, hydrogen fluoride reacts with phosphorus pentoxide to produce phosphorus pentafluoride and water. The water is absorbed by the highly hygroscopic P2O5 to form phosphoric acid liquid. The phosphoric acid liquid overflows from the reaction platform by its own weight and collects at the drain port. The phosphorus pentafluoride gas enters the dehydration device through the pipeline. At 40-60℃, the P2O5 laid on the inclined reaction platform of the dehydration device reacts with the small amount of water vapor carried by the phosphorus pentafluoride to produce phosphoric acid liquid. The phosphoric acid liquid overflows from the reaction platform by its own weight and collects at the drain port. The dry phosphorus pentafluoride gas (containing a small amount of HF and POF3) enters the POF3 condensation device through the pipeline. Here, the temperature is cooled to -40 to -50℃. HF and POF3 condense into liquid and solid, respectively, and are separated from PF5. The pure PF5 enters the lithium hexafluorophosphate reaction device through the pipeline.

[0013] Furthermore, both the PF5 generator and the dewatering unit are equipped with a transition chamber-type feeding port. When phosphorus pentoxide is consumed to a certain extent, it is replenished through the transition chamber without stopping production, thus ensuring continuous production.

[0014] Furthermore, to improve phosphorus source utilization, a phosphoric acid dehydration unit, also known as a phosphoric acid recovery and reuse unit, was designed. This unit has a tunnel-type structure, with a liquid inlet and a solid outlet located at opposite ends of the tunnel. A movable crucible is installed inside the tunnel to transport the material. The phosphoric acid liquid collected from the drain outlets of the PF5 generator and dehydration unit enters the phosphoric acid dehydration unit through pipelines and is loaded into the crucible. The phosphoric acid moves along the tunnel with the crucible and is heated to 200-300°C, decomposing and removing water to generate metaphosphoric acid. The metaphosphoric acid is then collected from the solid outlet of the tunnel and transferred to the PF5 generator, allowing it to continue participating in the reaction and thus fully utilizing the phosphorus source.

[0015] Furthermore, the POF3 separated by the aforementioned POF3 condensation device can be further fluorinated to generate PF5, which can be reused in the system without wasting resources.

[0016] In the lithium hexafluorophosphate preparation unit described above, lithium fluoride and anhydrous hydrogen fluoride are added to the LiF dissolving device to react and generate a LiHF2 solution. This solution is then transferred through a pipeline to a reaction device, where it reacts with phosphorus pentafluoride to generate a lithium hexafluorophosphate hydrogen fluoride solution. The lithium hexafluorophosphate solution is then transferred through a pipeline to a crystallization device, where it flows slowly along an S-shaped pipe and is subjected to stepped cooling. Simultaneously, under ultrasonic treatment, lithium hexafluorophosphate crystallizes out. The crystallized liquid is transferred through a pipeline to a separation device, where the crystals and liquid are separated. The crystals enter a drying device for further drying to obtain the lithium hexafluorophosphate product. The separated liquid then enters the LiF dissolving device through a pipeline to react with newly added lithium fluoride to generate a new LiHF2 solution. The combination of stepped cooling and ultrasonic treatment results in more uniform crystal particles and higher crystallization efficiency.

[0017] It is worth noting that lithium fluoride and anhydrous hydrogen fluoride are fully dissolved in the dissolution section before being transferred to the reaction section to react with phosphorus pentafluoride, completely eliminating the problem of lithium fluoride entrainment in the lithium hexafluorophosphate product. The lithium hexafluorophosphate solution flows and crystallizes simultaneously within the S-shaped pipe of the crystallization unit, ensuring continuous production and avoiding the discontinuous production issues of existing batch crystallization technologies. The entire production system can operate continuously and smoothly, without interruption during feeding or discharging, significantly improving production efficiency.

[0018] Compared with existing technologies, the lithium hexafluorophosphate continuous production system of this application includes key devices such as continuous phosphorus pentafluoride generation and continuous impurity removal, and continuous lithium hexafluorophosphate generation and continuous crystallization. It can achieve continuous production of lithium hexafluorophosphate with high efficiency, making it suitable for industrial applications. The PF5 generation device utilizes a narrow reaction chamber to improve hydrogen fluoride utilization. The gas discharged from the end of the reaction chamber is mainly phosphorus pentafluoride, with very little water vapor, hydrogen fluoride, and phosphorus trifluoride oxyfluoride. After further impurity removal by a dehydration device and a POF3 condenser, high-purity phosphorus pentafluoride is obtained. The PF5 generation device is equipped with an overflow ramp reaction platform, which automatically separates liquid reaction products by gravity, allowing exposed phosphorus pentoxide to continue reacting. This simplifies the equipment separation design, resulting in simpler equipment and lower application and maintenance costs. The PF5 dehydration device uses the same phosphorus pentoxide as the PF5 generation device to dehydrate phosphorus pentafluoride, without introducing impurities. Phosphoric acid, a byproduct of the PF5 generation and dehydration units, is partially dehydrated in a phosphoric acid dehydration unit to produce metaphosphoric acid, which can then be used as a raw material for the PF5 generation reaction, thus achieving comprehensive utilization of phosphorus resources. The PF5 generation unit, dehydration unit, and phosphoric acid dehydration unit work together to not only efficiently and cost-effectively produce phosphorus pentafluoride but also efficiently remove moisture. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the continuous production system for lithium hexafluorophosphate in this application.

[0020] In the diagram, 1 is the PF5 generating device, 2 is the dehydration device, 3 is the phosphoric acid dehydration device, 4 is the POF3 condensation device, 5 is the reaction device, 6 is the crystallization device, 7 is the separation device, 8 is the LiF dissolution device, and 9 is the drying device. Detailed Implementation

[0021] The technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0022] A continuous production system for lithium hexafluorophosphate includes a phosphorus pentafluoride preparation unit and a lithium hexafluorophosphate preparation unit. The phosphorus pentafluoride preparation unit includes a PF5 generator, a dehydration unit, a POF3 condenser, and a phosphoric acid dehydration unit. The lithium hexafluorophosphate preparation unit includes a reaction unit, a crystallization unit, a separation unit, a drying unit, and a LiF dissolution unit.

[0023] Both the PF5 generator and the dehydration device are equipped with a long and narrow reaction chamber. Inside the chamber, there is a ramp-type reaction platform with an overflow function. The reaction platform is used to support solid reaction raw materials. The air inlet and the exhaust outlet are respectively located at both ends of the long and narrow reaction chamber.

[0024] Furthermore, the inclined reaction platform has an angle of 15-45° with the horizontal plane, and the platform is treated with anti-slip material to prevent solid reactants from sliding under weight. The anti-slip treatment includes, but is not limited to, etching, sandblasting, and the addition of baffles.

[0025] The POF3 condensation device is a low-temperature condensation device. PF5 gas containing POF3 impurities is cooled to below the boiling point of POF3, and the POF3 impurities condense into liquid or solid and remain in the device, while PF5 flows out in gaseous form.

[0026] The phosphoric acid dehydration device is a tunnel type, with a liquid inlet and a solid outlet located at both ends of the tunnel. A movable sagger is installed inside the tunnel to carry the material.

[0027] The reaction device is equipped with a stirring paddle, and the crystallization device is equipped with multiple parallel S-shaped pipes, with an ultrasonic generator around the pipes.

[0028] When the above-mentioned continuous lithium hexafluorophosphate production system is working, solid P2O5 is placed on the sloping reaction platform of the PF5 generator. Hydrogen fluoride gas is introduced through the gas inlet. Under the condition of 150-250℃, hydrogen fluoride reacts with phosphorus pentoxide to produce phosphorus pentafluoride and water. The water is absorbed by the highly hygroscopic P2O5 to form phosphoric acid liquid. The phosphoric acid liquid overflows from the reaction platform by its own weight and collects at the drain port. The phosphorus pentafluoride gas enters the dehydration device through the pipeline. At 40-60℃, the P2O5 laid on the sloping reaction platform of the dehydration device reacts with the small amount of water vapor carried by the phosphorus pentafluoride to produce phosphoric acid liquid. The phosphoric acid liquid overflows from the reaction platform by its own weight and collects at the drain port. The dry phosphorus pentafluoride gas (containing a small amount of HF and POF3) enters the POF3 condensation device through the pipeline. Here, the temperature is cooled to -40 to -50℃, and HF and POF3 condense into liquid and solid, respectively, separating from PF5. The pure PF5 enters the lithium hexafluorophosphate reactor through the pipeline.

[0029] Simultaneously with the preparation of phosphorus pentafluoride, lithium fluoride and anhydrous hydrogen fluoride are added to the LiF dissolving device to react and generate a LiHF2 solution. This solution is then transferred through a pipeline to the reaction device, where it reacts with the phosphorus pentafluoride gas to generate lithium hexafluorophosphate, which dissolves in the hydrogen fluoride solution. The lithium hexafluorophosphate solution is then transferred through a pipeline to the crystallization device, where it flows slowly along an S-shaped pipe and is cooled in stages. Simultaneously, lithium hexafluorophosphate crystallizes out under ultrasonic action. The crystallized liquid is transferred through a pipeline to the separation device, where the crystals and liquid are separated. The crystals enter the drying device for further drying to obtain the lithium hexafluorophosphate product. The liquid then enters the LiF dissolving device through a pipeline to react with the newly added lithium fluoride to generate a new LiHF2 solution.

[0030] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A continuous production system for lithium hexafluorophosphate, comprising a phosphorus pentafluoride preparation unit and a lithium hexafluorophosphate preparation unit, characterized in that: The phosphorus pentafluoride preparation unit includes a PF5 generator, a dehydration device, a POF3 condensation device, and a phosphoric acid dehydration device. The exhaust port of the PF5 generator is connected to the air inlet of the dehydration device through a pipe, and the exhaust port of the dehydration device is connected to the air inlet of the POF3 condensation device through a pipe. Both the PF5 generator and the dehydration device are provided with a drain port, which is connected to the liquid inlet of the phosphoric acid dehydration device through a pipe. The solid outlet of the phosphoric acid dehydration device is connected to the inlet of the PF5 generator through a pipe. The lithium hexafluorophosphate preparation unit includes a LiF dissolving device, a reaction device, a crystallization device, a separation device, and a drying device. The exhaust port of the POF3 condensing device is connected to the air inlet of the reaction device through a pipe. The discharge port of the LiF dissolving device is connected to the feed inlet of the reaction device through a pipe. The discharge port of the reaction device is connected to the feed inlet of the crystallization device through a pipe. The discharge port of the crystallization device is connected to the feed inlet of the separation device through a pipe. The solid discharge port of the separation device is connected to the feed inlet of the drying device. The liquid discharge port of the separation device is connected to the feed inlet of the LiF dissolving device through a pipe. Both the PF5 generator and the dehydration device are equipped with a narrow reaction chamber. The narrow reaction chamber is equipped with a ramp-type reaction platform with overflow function. The ramp-type reaction platform is used to support solid reaction raw materials. The air inlet and the exhaust outlet are respectively located at both ends of the narrow reaction chamber.

2. The continuous lithium hexafluorophosphate production system according to claim 1, characterized in that, The angle between the surface of the inclined reaction table and the horizontal plane is 15-45°, and the surface is treated with anti-slip material.

3. The continuous lithium hexafluorophosphate production system according to claim 2, characterized in that, The anti-slip treatment is achieved through etching, sandblasting, or the addition of baffles.

4. The continuous lithium hexafluorophosphate production system according to claim 1, characterized in that, The POF3 condensation device is a low-temperature condensation device.

5. The continuous lithium hexafluorophosphate production system according to claim 1, characterized in that, The phosphoric acid dehydration device is a tunnel type, with a liquid inlet and a solid outlet located at both ends of the tunnel. A movable sagger is installed inside the tunnel to carry the material.

6. The continuous lithium hexafluorophosphate production system according to claim 1, characterized in that, The reaction device is equipped with a stirring paddle, and the crystallization device is equipped with multiple parallel S-shaped pipes, with an ultrasonic generator surrounding the pipes.

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