The Carbon-Free Ag Electrode for Non-Aqueous Li-O2 Batteries
There have been many attempts to prevent decomposition of the carbon materials in the air electrode during cycling.5 It has shown by density functional calculation that the structural defects in the carbon materials of the air electrode easily reacted with the electrolyte. It also demonstrated that Al2O3 coating on the carbon electrode by atomic layer deposition (ALD) prevented the decomposition of the tetraethylene glycol dimethyl ether (TEGDME) by blocking the reaction of the TEGDME solvent molecules with the defect sites on the carbon surface. D. M. Itkis’s group also confirmed that activated double bonds or aromatics of the carbon materials react with the oxygen radical on the epoxy groups and carbonates during discharge. Meanwhile, carbon-free materials of air electrodes: Ru/indium tin oxide (Ru/ITO) and TiC were investigated. The carbon-free materials indeed suppressed the formation of Li2CO3 and enhanced the rechargeability of Li-air batteries.
In this study, we employ Ag-coated air electrode prepared by electrodeposition. The electrodeposition is one of the simplest metal deposition methods and easily adaptable to a large scale production. Sun’s group have, in fact, applied the electrodeposition method to deposit Co3O4 on the air electrode for the first time. The Pt/Co3O4-deposited carbon-free electrode showed very low polarization during the charge process but high polarization during the discharge process. Since Ag has very high electronic conductivity and good catalytic property for the oxygen reduction reaction, it is surmised that the Ag-deposited electrode can potentially outperform the previously studied carbon-free materials of air electrodes.
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