Spinel NiCo2O4-Deposited CNT Bucky Paper As a Cathode for Rechargeable Li-O2 Battery

Abstract

There has been a great interest in the development of rechargeable batteries with high energy storage capability due to an increasing demand for electric vehicles (EVs) with driving ranges comparable to those of gasoline-powered vehicles. Among various types of batteries under development, a Li–oxygen(O2) battery delivers the highest theoretical energy density, thus, it is considered a promising energy storage technology for EV applications [1]. Cathode (oxygen electrode) is the key component of Li–O2 battery, since the major battery reactions i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) occur at its surface. However, low round-trip efficiency, poor reversibility and poor power capability are the major challenges faced by the cathodes of the Li–O2 battery [2]. Although the carbon has been generally considered as a good cathode material in Li-O2 batteries because of its advantages such as good chemical stability, high conductivity and versatile porosity, however, it may suffer from the corrosion/oxidation at high potentials in the charging process and promote the electrolyte decomposition accompanying various side reactions during cycling. Therefore, it is strongly required to find out the alternative cathodes to circumvent side reactions involving carbon based materials. To resolve this problem, one possible solution is to suppress the direct exposure of carbon surface to the aprotic electrolyte by uniform coating of non-carbon material on the carbon surface. In the present work, we report spinel NiCo2O4-deposited CNT (carbon nanotube) bucky paper as a cathode for Li-O2 batteries. To passivate the surface of CNT buckypaper to be attacked by Li2O2 and super radicals, the CNT bucky paper cathode was uniformly coated by metal-oxide (NiCo2O4) layer using simple hydrothermal method. The structural properties of the oxide-deposited CNT cathode are characterized and the electrochemical performances of Li-O2 battery constructed with that cathode are evaluated. The oxide-deposited CNT cathode shows high specific capacities and remarkably reduced charge potentials (in comparison with a carbon-only cathode) as well as excellent cyclability, which suggests that the deposited oxide layer on the surface of CNT effectively reduces the amount of carbonates generated on the surface of carbon. Reference [1] A. C. Luntz, B. D. McCloskey, Chem. Rev., 114 (2014) 11721. [2] I. Landa-Medrano, R. Pinedo, N. Ortiz-Vitoriano, I. R. Larramendi, T. Rojo, ChemSusChem, 8 (2015) 3932.