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

Abstract

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.