Metal Oxides as Sulfur Host Cathodes

Metal oxides are a major type of sulfur host which can substantially improve the electrochemistry of sulfur cathodes. Due to the presence of a strong polar surface, metal oxides can effectively adsorb polysulfides via chemical bonding, resulting in enhanced confinement of polysulfides. Besides, the abundant metal sites can catalyze the electrochemical conversion of sulfur species, effectively improving the reaction kinetics of Li–S batteries. However, the compromised conductivity of metal oxides is detrimental to the charge transfer of sulfur cathodes, impeding rapid redox conversion of Li–S batteries. Therefore, the design of metal oxide host materials that can confine sulfur species and accelerate their redox conversion kinetics has been a promising strategy for high-performance Li–S batteries. In this chapter, we first discuss the interactions between metal oxide hosts with sulfur, unraveling the underlying mechanisms of metal oxides towards the confinement and catalytic conversion of sulfur. Then various metal oxide hosts used in Li–S batteries are systematically summarized. Finally, the design strategies of metal oxide hosts are presented, including heterostructures, vacancies, and morphology engineering. This chapter can provide a cutting-edge insight into metal oxides as sulfur host cathodes.