Method for Manufacturing Lithium-Air Batteries Using F-Doped Carbon Cathodes

Surface Modification of Lithium-Air Battery Cathodes via In-Cell Electrochemical Reduction of LiTFSI

This technology induces an electrochemical reduction of the LiTFSI electrolyte salt within a lithium-air battery to perform in-situ fluorine (F) doping and carboxyl group formation directly on the carbon paper cathode surface.

In conventional lithium-air batteries, discharge products like Li2O2 clog cathode pores, reducing discharge capacity and lowering charge-discharge efficiency due to high overpotential during charging. Furthermore, limitations in external oxygen supply and electron/ion transport have hindered the realization of high power and high capacity.

This technology involves assembling the cell and applying a 0.05 mA current for 8–10 hours in an inert atmosphere to reduce LiTFSI, thereby introducing fluorine and carboxyl groups to the carbon paper surface. This increases oxygen affinity, secures O2 diffusion pathways, and expands active sites for Li2O2 formation. Applicable to ultra-high energy density power sources for drones and long-range mobility, as well as next-generation metal-air battery cathodes, it enables cathode functionalization simply by applying current after cell assembly, eliminating the need for separate doping equipment.

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Key Features:

• Cell manufacturing step: placing carbon paper as the cathode, lithium metal as the anode, and a separator and LiTFSI-containing electrolyte in between
• F-doping step: doping fluorine onto the carbon paper using the reduction reaction of LiTFSI that occurs during discharge in an inert atmosphere
• Doping discharge step: performed by applying a 0.05 mA current for 8–10 hours in an inert atmosphere
• Electrolyte for lithium-air batteries: utilizing 1 M LiTFSI dissolved in TEGDME solvent as the F-doping source

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This invention was developed with support from the Ministry of Education for the development of high-power lithium-air battery cathode materials.

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