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

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 5C. 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 acts 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.