Plasma-polymerized C60-coated CNT interlayer with physical and chemical functions for lithium–sulfur batteries

Abstract The electrochemical application of plasma-induced polymerized fullerene (PC60), wherein C60-derived radicals play physical and chemical functions, representing an important frontier in fullerene derivatives. We prepared a dual-functional interlayer of a gradationally PC60-coated carbon nanotube (CNT) matrix, where the population of C60-originating carbon moieties decreased linearly across the CNT@PC60 from the separator to the sulfur electrode in a lithium–sulfur battery (LSB). The three-dimensional CNT@PC60 interlayer acted as both a physical ionic shield, impeding the shuttle effect, and a catalytic immobilizer, enhancing the kinetics of sulfur conversion. The synergistic effectiveness of the dual perm-selective CNT@PC60 interlayers in confining polysulfide species enabled delivery by the LSB with a high specific capacity of 829 mAh g−1 and an ultra-low decay rate of 0.066% per cycle over 400 cycles at 5 C. The role of PC60 in this superior electrochemical performance is the different physical and chemical characteristics of the ends of the interlayer. The PC60-rich side as a physical barrier with a mean pore size of 0.7 nm, which enables the penetration of lithium ions only without polysulfide intrusion. Meanwhile, the PC60-poor side formed a catalytic immobilizer because of its higher chemical functionalized degree.