Manufacturing Lithium Hexafluorophosphate Products By The Reaction Of AHF & Phosphorus Pentachloride.

Lithium hexafluorophosphate (LiPF6) is a critical component of the electrolyte used in lithium-ion batteries, with applications in lithium-ion power batteries, lithium-ion energy storage batteries, and other everyday batteries.

It is an indispensable electrolyte for lithium-ion batteries in the near and medium term, with no immediate replacement in sight

Battery-grade lithium hexafluorophosphate products are produced utilizing hydrogen fluoride, phosphorus pentachloride, and lithium fluoride as the primary raw materials.

5HF+PCl5 → PF5+5HCl (PCl5 conversion rate is 99.99%, selectivity ≈100%)

PF5+LiF → HF+LiPF6 (LiF conversion 99.99%, selectivity ≈100%)

The process for synthesizing battery-grade lithium hexafluorophosphate involves two main steps:

1. Synthesis of phosphorus pentafluoride: Refined AHF is pumped into a phosphorus pentafluoride reaction kettle. Phosphorus pentachloride is then added, metered, and reacted in a stirring state to generate phosphorus pentafluoride gas and hydrogen chloride gas. These gases are then downstreamed into the lithium hexafluorophosphate reaction system.
2. Synthesis of lithium hexafluorophosphate: Refined AHF is put into a lithium hydrogen fluoride reactor, and lithium fluoride is added after being metered to produce lithium hydrogen fluoride solution. The lithium fluoride solution enters the lithium hexafluorophosphate reaction system in countercurrent and reacts with phosphorus pentafluoride gas to produce lithium hexafluorophosphate. The resulting solution becomes the saturated solution of lithium hexafluorophosphate in AHF solution. HCl-entrained HF gas is output from the lithium hexafluorophosphate reaction kettle and separated into HF solution and HCl gas by a gas separation tower. The HF solution is then rectified into high-purity AHF and returned to the lithium hydrogen fluoride reactor.
3. Crystallization: The saturated solution of lithium hexafluorophosphate is pumped to a filter and then pre-cooled before being introduced into a circulating automatic crystallizer for deep cooling crystallization. The resulting crystals fall into a concentrator after crystal growth and concentration into a slurry. This slurry then enters a sealed centrifugal separation device for solid-liquid separation to obtain lithium hexafluorophosphate crystals with AHF on the surface. The mother liquor obtained by centrifugation is then returned to the crystallization system.
4. Drying and packaging: The lithium hexafluorophosphate crystal containing AHF is introduced into an air dryer, where the AHF is removed under the protection of N2, PF5, and F2 (commonly known as "drying"). The resulting lithium hexafluorophosphate is then cooled, introduced into the finished lithium hexafluorophosphate warehouse, and packaged into products in a dry and clean packaging environment. The dried gas from the airflow is condensed, and the HF gas is condensed into a liquid that is mixed with the raw material AHF, and the HF is recovered. The remaining gas is then compressed, dehumidified, heated, and supplemented with F2/N2 before being recycled.
5. Tail gas treatment: The entire system operates under slight negative pressure, and all tail gas is treated by a tail gas absorption device. Firstly, a calcium hydroxide emulsion is sprayed, and calcium fluoride sludge is separated from the solid and liquid. Then, dilute sodium hydroxide solution is sprayed, followed by clear water. After multiple cleanings, the tail gas reaches the discharge standard.
6. Wastewater treatment: Sodium hydroxide spray liquid reacts with calcium hydroxide emulsion to generate calcium fluoride precipitate. The solid-liquid separation is carried out to obtain calcium fluoride sludge and supernatant. The supernatant is used to dissolve sodium hydroxide, and clear water spray liquid is used to prepare calcium hydroxide emulsion. The surplus part is reused as clear water spray after membrane treatment, and the concentrated water produced by membrane treatment is mixed with calcium hydroxide emulsion.