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US-12617680-B2 - Synthesis of lithium-rich iron sulfides by chemical lithation

US12617680B2US 12617680 B2US12617680 B2US 12617680B2US-12617680-B2

Abstract

Disclosed herein is a method of: providing a polyaromatic hydrocarbon-M adduct solution and reacting the adduct with a sulfide compound having the formula Ni x Fe 1-x S 2 to form a product having the formula M y Ni x Fe 1-x S 2 . M is lithium or sodium. The value x is at least 0 and less than 1, and y is a positive number of at most 2. Also disclosed herein is a composition comprising M y Ni x Fe 1-x S 2 . The M y Ni x Fe 1-x S 2 has a particle size of less than 1 μm.

Inventors

  • Ryan H. DeBlock
  • Jeffrey W. Long
  • Hunter O. Ford
  • Debra R. Rolison
  • Brian L. Chaloux

Assignees

  • THE GOVERNMENT OF THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE SECRETARY OF THE NAVY

Dates

Publication Date
20260505
Application Date
20251006

Claims (13)

  1. 1 . A method comprising: providing a polyaromatic hydrocarbon-M adduct solution; wherein M is lithium or sodium; and reacting the adduct with a sulfide compound having the formula Ni x Fe 1-x S 2 to form a product having the formula M y Ni x Fe 1-x S 2 ; wherein x is at least 0 and less than 1; and wherein y is a positive number of at most 2.
  2. 2 . The method of claim 1 , wherein the sulfide compound is FeS 2 .
  3. 3 . The method of claim 2 ; wherein the iron sulfide is in the form of a coating on a substrate; and wherein reacting the benzophenone-lithium adduct with the iron sulfide comprises adding the substrate to the benzophenone-lithium adduct solution.
  4. 4 . The method of claim 3 , wherein the substrate is a carbon substrate.
  5. 5 . The method of claim 4 , wherein the carbon substrate is a carbon fiber.
  6. 6 . The method of claim 4 , wherein the carbon substrate is a carbon paper comprising pores and having the iron sulfide deposited within the pores.
  7. 7 . The method of claim 3 , wherein the substrate is a metal substrate.
  8. 8 . The method of claim 2 , wherein the product is Li y FeS 2 having a particle size of less than 1 μm.
  9. 9 . The method of claim 2 , wherein the product is Li y FeS 2 having a particle size of less than 10 nm.
  10. 10 . The method of claim 1 , further comprising: providing a benzophenone solution; adding lithium metal or sodium metal to the benzophenone solution to form a benzophenone-M adduct solution; wherein the benzophenone-M adduct is [(C 6 H 5 ) 2 CO]·M + .
  11. 11 . The method of claim 10 , wherein the benzophenone solution comprises diethylene glycol dimethyl ether.
  12. 12 . The method of claim 10 , wherein up to 2 mol of the lithium metal per 1 mol of the benzophenone is added to the benzophenone solution.
  13. 13 . The method of claim 1 , wherein the polyaromatic hydrocarbon is benzophenone.

Description

REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63/703,264, filed on Oct. 4, 2024. The provisional application and all other publications and patent documents referred to throughout this nonprovisional application are incorporated herein by reference. TECHNICAL FIELD The present disclosure is generally related to lithium-rich iron sulfides. DESCRIPTION OF THE RELATED ART Charge-insertion cathodes utilized in lithium-ion batteries (LIBs) rely on topotactic insertion and deinsertion of Li+ into/from the material concomitant with transition-metal reduction and oxidation, respectively.1 This insertion reaction is typically limited to a one-electron transfer, determined by the moles of Li+ in the cathode material and the available oxidation states in its transition metal. Recently, a class of lithium-rich oxides (e.g., Li2RuO3 and Li2MnO3) has demonstrated both cationic (metal-based) and anionic (oxygen-based) redox upon lithium insertion that can effectively double the capacity for a given material.2,3 Research on the anion-redox mechanism predominantly focuses on characterizing and optimizing oxide-based materials. Due to the high voltages at which oxide-based anion redox is active, charge-storage processes may compete with undesirable reactions such as electrolyte degradation and irreversible evolution of CO2, CO, and O2.4,5 In contrast with Li-rich oxide materials, analogous metal sulfides oxidize at lower and more practical voltages due to the higher energy of their frontier orbitals.6-8 These alkali-rich chalcogenides present an attractive opportunity to avoid electrolyte breakdown, eliminate unsafe O2 evolution, and provide a more stable electrochemical window in which to operate while still utilizing anionic-redox mechanisms. One promising cathode composition, lithium-rich iron sulfide, Li2FeS2, stores 1.5 to 2 electrons per formula unit through the combination of cationic and anionic redox, increasing the achievable cathode capacity to nearly 400 mAh g−1.9,10 In contrast, lithium nickel manganese cobalt oxide (NMC) and nickel cobalt aluminum oxide (NCA) cathodes found in state-of-the-art LIBs typically exhibit a capacity of ˜200 mAh g−1.11 The synthesis of lithium-rich iron sulfide and related materials has historically been limited to high-temperature (>880° C.), solid-state methods that typically involve grinding and heating precursor materials (e.g., FeS2, Fe, and Li2S powders) to their molten state.9,10,12,13 After cooling back to ambient temperature, the resulting materials are chunky particulates (tens of micrometers) that are difficult to further process into powder-composite electrodes for battery use. This melt-based approach also limits synthetic control for desired compositional variations (e.g., metal-site substitution for Fe in Li2FeS2) as restricted by the melting points of other available metal precursors. SUMMARY OF THE INVENTION Disclosed herein is a method comprising: providing a polyaromatic hydrocarbon-M adduct solution and reacting the adduct with a sulfide compound having the formula NixFe1-xS2 to form a product having the formula MyNixFe1-xS2. M is lithium or sodium. The value x is at least 0 and less than 1, and y is a positive number of at most 2. Also disclosed herein is a composition comprising MyNixFe1-xS2. M is lithium or sodium. The value x is at least 0 and less than 1, and y is a positive number of at most 2. The MyNixFe1-xS2 has a particle size of less than 1 μm. BRIEF DESCRIPTION OF DRAWINGS A more complete appreciation will be readily obtained by reference to the following Description of the Example Embodiments and the accompanying drawings. FIG. 1 shows a synthesis schematic of the chemical lithiation of pyrite and its transformation into Li2FeS2. FIG. 2 shows X-ray diffractograms (Cu Kα radiation; λ=1.5406 Å) of pyrite FeS2 precursor, Li2FeS2:s.s., Li2FeS2:c.l., and Li2FeS2:c.l.800. FIG. 3 shows inductively coupled plasma-optical emission spectrometry (ICP-OES) results for chemically lithiated Li2FeS2. The final composition determined by the elemental assay of the material is Li1.95FeS2.18 by assuming that all sulfur is lost to H2S generation during air exposure and dissolution in nitric acid. FIGS. 4A-D show scanning electron micrographs of pyrite FeS2 precursor (FIG. 4A), Li2FeS2:s.s. (FIG. 4B), Li2FeS2:c.l. (FIG. 4C), and Li2FeS2:c.l.800 (FIG. 4D) powders. Scale bar=25 μm. FIGS. 5A-B shows voltammetric sweep (0.1 mV s−1) (FIG. 5A) and galvanostatic charge/discharge (20 mA g−1) (FIG. 5B) of Li2FeS2:c.l.800 between 1.8-3.0 V in a half-cell configuration. FIG. 6 shows discharge capacity retention of Li2FeS2:c.l.800 for increasing C-rate (based on 1 e− redox; 200 mAh g−1). FIG. 7 shows cycling retention of Li2FeS2:c.l.800 at 0.25C (based on 1 e− redox; 200 mAh g−1). FIG. 8 shows a comparison of galvanostatic charge/discharge (20 mA g−1) for Li2FeS2:c.l., Li2FeS2:c.l.800, and Li2FeS2:s.s. in a half-cell configur