Enhanced potential of amorphous electrode materials: Case study of RuO 2

Abstract

The excess free energy of amorphous RuO2 that occurs in Li cells with RuO2 cathodes was studied after a deep discharge/charge cycle. The 10μm sized RuO2 was obtained by heat treatment of 60 nm RuO2 at 800°C for 50 hr in air. The results show that the RuO2 phase obtained upon oxidation of the Ru/Li2O composite is an amorphous phase, while the nanocrystalline RuO2 is only formed upon electron beam exposure. A significantly curved discharge behavior of RuO2 for the effect of nanosize on the discharge/charge curves is observed at higher potential. It is found that for the large grain size of 10 μm, the discharge rate of C/20 is not sufficiently slow to reach thermodynamic equilibrium and leads to a potential of about 1.15 V.