Lamellar Iron Sulfides with Embedded Cations for Electrical Energy Storage

SUMMARY

• Electrodes in supercapacitor devices (computers, electric/fossil fuel burning vehicles, and renewable energy storage) and electrodes in lithium (Li) and sodium (Na) batteries (portable electronic devices, grid energy storage applications, and electric vehicles) can all benefit from improvements in their ability to store/produce energy/charge in a more efficient and sustainable manner. Various electrode materials have been investigated to improve upon supercapacitor and Li/Na battery performance, including pyrite and other iron sulfide (FeS) based materials (e.g., mackinawite, smythite).

• The inventors have developed a new lamellar FeS material; Fe(DEDTC)3 + LiOTf with a layered structure produced by solvothermal decomposition of either tris(dialkyldithiocarbamato) iron(III) or tris(alkylxanthato) iron(III), or by reacting a synthetic 4Fe‐4S cluster with oxidizing agents. The material is fabricated in either a bulk powder or as a thin film (TF) deposited on a substrate material.

• As tested in the laboratory, the powder when formed into a slurry through mixing with a polymer binder and solvent, and the TF coated substrate exhibited pseudocapacitive electrochemical behavior over a potential window of 1 V, with a specific capacitance of 100 F/g (for the Li synthesized material). The 100 F/g specific capacitance of this novel material is comparable to other investigated supercapacitor materials. The bulk powdered material exhibited electrical conductivity of 0.5 S/cm.

• Additional proof-of-concept laboratory experiments of the Fe(DEDTC)3 + LiOTf material indicated potential use as an electrode in Li/Na batteries by virtue of its high initial capacitance of between 800-1000 mAh/g, which is greater than materials used in commercial Li batteries.

FIGURE

ADVANTAGES

ADVANTAGES

• Increased levels of capacitor charge storage via enhanced ion intercalation
• Na ion battery electrodes for increased electrical storage
• Improved supercapacitor charge storage

PUBLICATIONS

• Horwitz, N. E. et al. Synthesis, modular composition, and electrochemical properties of lamellar iron sulfides. J Mater Chem A Mater 8, 15834–15844 (2020).