Electrochemical energy storage devices for automotive application have been significantly increasing because of the commercialization of plug-in hybrid vehicle (PHV) or electric vehicle (EV). Lithium/air rechargeable batteries are attracting great attention, because of a possibility to achieve energy density which is comparable to ICE.  Most of the studies recently reported were focusing on the non-aqueous system based on the following reaction. The reaction product Li2O2 deposits at the surface of the air electrode. 2Li+ + O2 + 2e ? Li2O2                (1)On the other hand, in the aqueous based Li-air system, the reaction product (LiOH�H2O) in the following equation is soluble into the electrolyte solution.  4Li+ + O2 +6H2O + 4e ? 4LiOH�H2O      (2)Therefore we have been investigating the aqueous based rechargeable Li-O2 batteries as a more practical battery system.  One of the key challenges of the aqueous system is the low output power of the protected lithium electrode. This type electrode has been preliminarily addressed by the invention of a composite lithium anode with three-layered structure by Visco et al. in 2004. Our lithium electrode adopts a lamination of NASICON-type lithium conducting solid electrolyte (LATP) and PEO-based polymer electrolyte, as the protect layers which covers and isolates lithium metal from contacting directly with aqueous electrolytes. One main approach to enhance electrode kinetics is the additives plasticizing polymer matrix. The study reports on ether-oligomer additives, e.g., tetraethylene glycol dimethyl ether (TEGDME) to PEO18LiTFSI. The electrical conductivity, interface resistance, polarizations and the lithium dendrite formation have been examined. The electrode/electrolyte interface resistance was decreased and maximum current density of 4 mAcm-2 can be applied. A Li/PEO18LiTFSI-2TEGDME/LATP/saturated LiCl aqueous solution/Pt, air cell showed stable cyclability up to 100 cycles at 2.0 mAh cm-2 of capacity.

Protected lithium electrode for aqueous lithium/air rechargeable batteries

247th National Meeting (2014)

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