A lightweight and binder-free electrode enabled by lignin fibers@carbon-nanotubes and graphene for ultrastable lithium-sulfur batteries

Realizing high sulfur loading while ensuring high sulfur utilization holds the key to enhancing the practical energy density of Li-S batteries. Inspired by the reinforced concrete structure in buildings, a facile route for the synthesis of a lightweight and binder-free electrode, composed of lignin fibers@carbon nanotubes as sulfur hosts and graphene as the current collector, was reported. Benefiting from the efficient polysulfide-anchoring performance of lignin fiber, 3D conductive frameworks of CNTs and the depolarization effect of graphene, the Li-S batteries using this electrode exhibited an unprecedented discharge capacity as high as 1632 mA h g(-1) at 0.1C and enhanced capacity of 987 mA h g(-1) after 500 cycles at 1.0C. Furthermore, even up to a sulfur loading of 9.2 mg cm(-2), this electrode still maintained a highly reversible capacity of 668.8 mA h g(-1) at 0.5C after 100 cycles, corresponding to 91.5% capacity retention. This lightweight and flexible electrode appears to be a scalable solution for obtaining high energy density Li-S batteries.