Sustainable and scalable methods for lithium metal production via hydrogen plasma reduction and lithium hydride discharging

Abstract

Methods are disclosed for the sustainable and scalable production of lithium metal. In one method, lithium salts such as lithium chloride are reduced using low-temperature hydrogen plasma to form lithium metal and lithium hydride. In another method, lithium hydride is thermally decomposed under vacuum or subjected to self-discharging in an AI / LiH / Pd circuit to yield lithium metal. The processes reduce harmful emissions, operate at lower temperatures than molten salt electrolysis, and produce high-purity lithium metal suitable for use in lithium-ion batteries.

Description

SUSTAINABLE AND SCALABLE METHODS FOR LITHIUM METAL PRODUCTION VIA HYDROGEN PLASMA REDUCTION AND LITHIUM HYDRIDE DISCHARGINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to 63 / 705,932, filed October 10, 2024, the contents of which are incorporated herein by reference in their entirety.FIELD OF THE INVENTION

[0002] The present invention relates to methods of manufacturing lithium metal, and more specifically, to sustainable and scalable techniques for producing lithium metal for lithium-ion battery applications through hydrogen plasma reduction of lithium salts and controlled discharging of lithium hydride.BACKGROUND OF THE INVENTION

[0003] Lithium metal is widely used in primary lithium batteries, advanced lithium- ion batteries for pre-lithiation, and as anode material in next-generation energy storage devices. Current commercial lithium metal production methods primarily involve electrolysis of molten lithium salts such as lithium chloride. However, such processes suffer from significant environmental and technical drawbacks, including:- High energy consumption and associated carbon emissions.- Generation of hazardous chlorine gas byproducts.- Requirements for anhydrous, inert processing conditions.- Complex packaging and storage due to lithium’s high reactivity.

[0004] The electroextraction of lithium metal from molten salts presents further challenges related to cost, operational safety, and scalability. There is an urgent need for sustainable and energy-efficient lithium metal production technologies.SUMMARY OF THE INVENTION

[0005] The present invention provides environmentally friendly and scalable methods for manufacturing lithium metal by:1. Hydrogen Plasma Reduction of Lithium Salts — Direct reduction of lithium chloride and other lithium salts using low-temperature hydrogen plasma to produce lithium metal and lithium hydride.2. Thermal and Electrochemical Conversion of Lithium Hydride — Controlled decomposition of LiH into lithium metal and hydrogen under vacuum, and selfdischarging of LiH in AI / LiH / Pd circuitry to yield lithium metal.

[0006] These methods reduce or eliminate chlorine gas emissions, require significantly lower operating temperatures than molten salt electrolysis, and are compatible with existing manufacturing infrastructure.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 — Photograph of LiCI after 1-hour hydrogen plasma treatment showing purple coloration.

[0008] Figure 2 — PXRD patterns of LiCI before and after hydrogen plasma treatment.

[0009] Figures 3-5 — PXRD patterns of LiOH, Li2CO3, and Li2O before and after hydrogen plasma treatment.

[0010] Figure 6 — High-purity LiCI before and after 4-hour hydrogen plasma treatment.

[0011] Figure 7 — PXRD of aggregate and residue after heating treated LiCI at 180 °C.

[0012] Figure 8 — LiH before and after vacuum heat treatment at 200 °C.

[0013] Figure 9 — TGA curves of treated and untreated LiH in nitrogen.

[0014] Figure 10 — PXRD of LiH before and after vacuum treatment.

[0015] Figure 11 — Energy and structure diagram of AI / LiH / Pd discharging circuit.

[0016] Figures 12-14 — PXRD of LiH after various discharging conditions.

[0017] Figure 15 — PXRD comparison showing lithium metal peaks from both LiH discharging and hydrogen plasma LiCI reduction.DETAILED DESCRIPTION OF THE INVENTION

[0018] The invention will now be described in detail with reference to certain embodiments. It will be understood that these embodiments are illustrative only and that variations and modifications in form, detail, and operation may be made without departing from the spirit and scope of the invention as claimed.

[0019] Overview:In one aspect, the invention provides methods for producing lithium metal through:1. Hydrogen plasma reduction of lithium salts to form lithium hydride (LiH) and lithium metal.2. Thermal and electrochemical conversion of lithium hydride to lithium metal.

[0020] Materials:In various embodiments, the lithium source may be selected from lithium halides, lithium hydroxide, lithium oxide, and lithium carbonate, with purities ranging from about 95% to about 99.999%. Hydrogen gas may be supplied at flow rates from about 10 seem to about 30 seem. The plasma source may be operated at a power setting between about 10% and about 30%.

[0021] Hydrogen Plasma Reduction Process:A lithium salt is placed in a low-temperature hydrogen plasma reactor under hydrogen flow for 0.5-6 hours. Lithium chloride produces lithium metal and lithium hydride, confirmed by PXRD peaks at hkl (110) and (200) and LiH peaks. Other salts may require up to 12 hours.

[0022] Post-Plasma Thermal Processing:Lithium hydride from the plasma process is heated under vacuum at 150-250 °C, preferably 180-200 °C, for 4-12 hours to form lithium metal.

[0023] Electrochemical Conversion of LiH to Lithium Metal:Lithium hydride is placed between a palladium anode and aluminum cathode, heated under vacuum at 70-100 °C, and subjected to 5-50 V to produce lithium metal.

Claims

WHAT IS CLAIMED IS:1 . A method for producing lithium metal, comprising: a) providing a lithium salt selected from the group consisting of lithium chloride, lithium hydroxide, and lithium carbonate; b) subjecting the lithium salt to low-temperature hydrogen plasma at a hydrogen flow rate between 10-30 seem and a power between 10-30% for a period of 0.5-6 hours, thereby producing lithium hydride and lithium metal; and c) isolating the lithium metal under inert or vacuum conditions.

2. The method of claim 1 , wherein the lithium salt is lithium chloride having a purity of at least 99%.

3. The method of claim 1 , further comprising heating the lithium hydride under vacuum at a temperature between 150-250 °C to produce lithium metal.

4. A method for producing lithium metal from lithium hydride, comprising: a) placing lithium hydride between a palladium anode and an aluminum cathode; b) heating the assembly under vacuum to a temperature between 70-100 °C; c) applying a potential difference between 5-50 volts across the electrodes; and d) recovering lithium metal formed at the cathode.

5. The method of claim 4, wherein the palladium anode is replaced with copper in certain embodiments.

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