Process

Abstract

A process for at least partially converting a bis (fluorosulfonyl) imide (HFSI) to a metal bis (fluorosulfonyl) imide (MHFSI), comprising: feeding a composition comprising a metal bicarbonate, a solvent, and a component comprising the bis (fluorosulfonyl) imide into a reactor to form a blend thereof; and reacting the metal bicarbonate with a bis (fluorosulfonyl) imide.

Description

Technical Field

[0001] The present invention relates to a method for preparing a metal salt of bisfluorosulfonyl imide, and the method is particularly suitable for preparing lithium bisfluorosulfonyl imide. Background Art

[0002] Lithium salts, such as lithium bis(fluorosulfonyl)imide (LiFSI), are used in batteries, such as commercial secondary batteries, taking advantage of their high solubility in non-aqueous polar solvents. LiFSI is used as an electrolyte in lithium-ion batteries.

[0003]

[0004] Currently, lithium bicarbonate manufacturing is carried out by converting bis(fluorosulfonyl)imide (HFSI) into LiFSI via reaction with lithium carbonate (Li2CO3).

[0005] However, the synthesis of LiFSI requires multiple filtration steps to separate the product from the reactants. This is primarily due to the use of an insoluble lithium source, Li2CO3. This reduces the potential final yield of the product.

[0006] Therefore, there is a need for an improved method for producing lithium bicarbonate. Summary of the Invention

[0007] According to a first aspect of the present invention, there is provided a method for at least partially converting bisfluorosulfonyl imide (HFSI) into metal bisfluorosulfonyl imide (MHFSI), comprising:

[0008] feeding a composition comprising a metal bicarbonate, a solvent, and a component comprising a bisfluorosulfonyl imide into a reactor to form a blend thereof; and

[0009] The metal bicarbonate is reacted with the bisfluorosulfonyl imide.

[0010] Typically, the bisfluorosulfonyl imide (HFSI) is at least partially converted to the metal bisfluorosulfonyl imide (MHFSI). The conversion rate is preferably or close to 100%. Any unconverted bisfluorosulfonyl imide (HFSI) is preferably recycled back to the reaction via a recycling and / or purification step.

[0011] Optionally, the process comprises a stage of preparing a bisfluorosulfonyl imide. Preferably, the bisfluorosulfonyl imide is prepared by reacting bischlorosulfonyl imide with a fluorinating agent, preferably comprising HF.

[0012] Therefore, according to a second aspect of the present invention, there is provided a method for preparing metal bisfluorosulfonimide (MHFSI), comprising:

[0013] a) at least partially converting bischlorosulfonyl imide into bisfluorosulfonyl imide (HFSI), the at least partial conversion comprising:

[0014] feeding a composition comprising bischlorosulfonimide and a fluorinating agent into a reactor to form a blend thereof; and

[0015] reacting the bischlorosulfonimide with a fluorinating agent; and

[0016] b) at least partially converting the bisfluorosulfonyl imide (HFSI) into a metal bisfluorosulfonyl imide (M HFSI), wherein the at least partial conversion comprises:

[0017] feeding a composition comprising a metal bicarbonate, a solvent, and a component comprising a bisfluorosulfonyl imide into a reactor to form a blend thereof; and

[0018] The metal bicarbonate is reacted with the bisfluorosulfonyl imide.

[0019] Typically, the bisfluorosulfonyl imide (HFSI) is at least partially converted to the metal bisfluorosulfonyl imide (MHFSI). The conversion rate is preferably or close to 100%. Any unconverted bisfluorosulfonyl imide (HFSI) is preferably recycled back to the reaction via a recycling and / or purification step.

[0020] The components of each aspect of the present invention will be described below. It should be understood that the components described are equally applicable to either / both aspects mutatis mutandis.

[0021] The metal bicarbonate salt and the solvent preferably form a solution / suspension. The metal bicarbonate salt and the solvent most preferably form a solution.

[0022] Most preferably, the metal bicarbonate is or comprises lithium bicarbonate.

[0023] Most preferably, the solvent for the metal bicarbonate is or comprises water.

[0024] The process of the present invention has been found to be advantageous because it allows for easy and cost-effective production of metal bis(fluorosulfonyl)imides. The process is extremely simple. It does not require the intermediate filtration step associated with some prior art methods. Eliminating this step limits the loss of metal bis(fluorosulfonyl)imide during the process.

[0025] In addition, it has been found that the overall efficiency of the metalation (lithiation) reaction is improved. This is suspected to be due to the complete dissolution of the metal bicarbonate (preferably lithium bicarbonate).

[0026] Preferably, in the bisfluorosulfonyl imide preparation portion of the process, the bischlorosulfonyl imide is added to the reactor as a suspension / solution. Preferably, acetonitrile is used as the solvent in the suspension / solution. The concentration of the bischlorosulfonyl imide is preferably about 33 wt%.

[0027] Preferably, the fluorinating agent comprises HF. Preferably, the fluorinating agent is used in excess for fluorination. The reactor is preferably released during the reaction. After the reaction, the reactor is preferably vented with an inert gas (such as nitrogen) to remove HCl formed during the reaction.

[0028] In view of the aggressive nature of most fluorinating agents (and particularly HF), the bisfluorosulfonimide preparation portion of the process is preferably carried out in a reactor formed of, or at least coated with, a corrosion resistant material such as Hastelloy.

[0029] After the reaction, the product is transferred to the metallization portion of the process. In the metallization portion of the process, the bis(fluorosulfonyl)imide solution is preferably added to the metal bicarbonate solution / suspension. The metal bicarbonate solution concentration is preferably 0.5 M to 0.8 M. The two reagents are allowed to react.

[0030] The product metal bisfluorosulfonyl imide is preferably extracted from the reaction product blend using a solvent. A preferred solvent is ethyl acetate.

[0031] The invention is illustrated with reference to the following non-limiting examples. DETAILED DESCRIPTION

[0032] Example 1 - Preparation LiFSI

[0033] Step 1 - Preparation of bis(fluorosulfonyl)imide

[0034] In a nitrogen-purged glove box, bis(chlorosulfonyl)imide (HClSI) (25 g) and acetonitrile (50 mL) were sealed in a 450 mL Hoechst alloy autoclave. The autoclave was transferred to the reactor stand and pressure-tested to 30 bar with nitrogen. After the pressure test, nitrogen was purged and HF (10 g) was transferred to the autoclave. The mixture was stirred at 10°C for 16 hours. After 16 hours, the formed HCl and excess HF were purged from the reactor with a nitrogen stream. The solution was transferred to a fluoropolymer container.

[0035] Step 2- preparation LiFSI

[0036] The mixture obtained in step 1 was added dropwise to a solution of LiHCO 3 in deionized water (1 L, 0.5 M-0.8 M).

[0037] The formed aqueous solution of LiFSI was concentrated to 200 mL of liquid.

[0038] LiFSI was extracted with three 200 ml portions of ethyl acetate. The organic layer was concentrated by solvent extraction to produce a solution of LiFSI in ethyl acetate.

Claims

1. A method for at least partially converting a bisfluorosulfonyl imide (HFSI) into a metal bisfluorosulfonyl imide (MHFSI), comprising: feeding a composition comprising a metal bicarbonate, a solvent, and a component comprising a bisfluorosulfonyl imide into a reactor to form a blend thereof; and The metal bicarbonate is reacted with a bisfluorosulfonyl imide.

2. A method for preparing metal bis(fluorosulfonyl)imide (MHFSI), comprising: a) at least partially converting bischlorosulfonyl imide into bisfluorosulfonyl imide (HFSI), the at least partial conversion comprising: feeding a composition comprising bischlorosulfonimide and a fluorinating agent into a reactor to form a blend thereof; and reacting the bischlorosulfonimide with a fluorinating agent; and b) converting the bisfluorosulfonyl imide (HFSI) at least partially into metal bisfluorosulfonyl imide (MHFSI), wherein the at least partial conversion comprises: feeding a composition comprising a metal bicarbonate, a solvent, and a component comprising a bisfluorosulfonyl imide into a reactor to form a blend thereof; and The metal bicarbonate is reacted with a bisfluorosulfonyl imide.

3. The method according to claim 1 or 2, wherein the metal bicarbonate and solvent form a solution.

4. The method of claim 1, 2 or 3, wherein the metal bicarbonate is or comprises lithium bicarbonate.

5. The method of any one of claims 1 to 4, wherein the solvent for the metal bicarbonate comprises water.

6. The process according to any one of claims 2 to 5, wherein the bischlorosulfonimide is added to the reactor in the form of a suspension / solution.

7. The process according to claim 6, wherein acetonitrile is used as solvent in the suspension / solution.

8. The method of any one of claims 2 to 7, wherein the fluorinating agent comprises HF.

9. A process according to any one of claims 1 to 8, wherein in the metallisation part of the process a bisfluorosulfonyl imide solution is added to the metal bicarbonate solution / suspension.

10. The process of any one of claims 1 to 8, wherein the product metal bisfluorosulfonimide is extracted from the reaction product blend with a solvent.

11. A metal bis(fluorosulfonyl)imide produced by the method according to any one of claims 1 to 10.

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