(Invited) Development of Porous Structures for Electrochemical Energy Storage

Abstract

We discuss the development of porous structures for the storage of electrochemical energy. Challenges in designing gas-diffusion electrodes for aqueous fuel cells are well known. Extending the use of oxygen electrode to a reversible metal-oxygen battery operating in aprotic media faces further difficulties. They include sluggish kinetics, components degradation, and formation of insulating solid oxide with irreversible structural changes. We synthesize carbon electrodes with controlled hierarchical porosity to investigate the impact of pore structure on performance. Using hierarchical porous carbon electrodes, investigations are carried out for electrocapacitance [1], the oxygen reduction reaction(ORR) in aqueous fuel cells,[2] and the cathode of an aprotic Li-O2 battery[3]. Results observed for Li-O2 has a capacity reaching 1/3 the theoretical energy density. The good performance of a Fe-N-doped hierarchical mesoporous carbon electrode are attributed to: i) A well-defined core-shell mesoporous structure for mass transport and dispersion of Li2O solid; ii) the Fe-N doping of carbon for corrosion resistance and improved conductivity; and iii) small and amorphous RuO2 for effective decomposition of Li2O. Challenges in electrodes for the sodium-oxygen battery technology are different and also discussed. The economic production of mesoporous materials is important for deployment of energy storage technologies in large scale. We also discuss the use of combustion techniques for the synthesis of porous metal oxides.[4,5] Li, M. Morris and K.Y. Chan, J. Mater. Chem. 21 (2011) 8880-8886.M. Zhou, C. Yang, K.Y Chan, Adv. Energy Mater., 4 (18), (2014) 1400840.M. Zhou, C.Y.V. Li, and K.Y. Chan, Energy Technology, 5 (2017) 732-739.A. Voskanyan, K.Y. Chan, and C.Y.V. Li, Chem. Mater. 28(8), (2016) 2768-2775.A.A. Voskanyan and K.Y. Chan, ACS Applied Nano Materials 1(2) (2018) 556-563.