The Fusion of Imidazolium-Based Ionic Polymer and Carbon Nanotubes: One Type of New Heteroatom-Doped Carbon Precursors for High-Performance Lithium-Sulfur Batteries

Rational design of sulfur host materials with high electrical conductivity and strong polysulfides (PS) confinement is indispensable for high-performance lithium-sulfur (Li-S) batteries. This study presents one type of new polymer material based on main-chain imidazolium-based ionic polymer (ImIP) and carbon nanotubes (CNTs); the polymer composites can serve as a precursor of CNT/NPC-300, in which close coverage and seamless junction of CNTs by N-doped porous carbon (NPC) form a 3D conductive network. CNT/NPC-300 inherits and strengthens the advantages of both high electrical conductivity from CNTs and strong PS entrapping ability from NPC. Benefiting from the improved attributes, the CNT/NPC-300-57S electrode shows much higher reversible capacity, rate capability, and cycling stability than NPC-57S and CNTs-56S. The initial discharge capacity of 1065 mA h g(-1) is achieved at 0.5 C with the capacity retention of 817 mA h g(-1) over 300 cycles. Importantly, when counter bromide anion in the composite of CNTs and ImIP is metathesized to bis(trifluoromethane sulfonimide), heteroatom sulfur is cooperatively incorporated into the carbon hosts, and the surface area is increased with the promotion of micropore formation, thus further improving electrochemical performance. This provides a new method for optimizing porous properties and dopant components of the cathode materials in Li-S batteries.