Polyfurfuryl alcohol-derived hierarchical porous carbon as high-performance cathodes for lithium-sulfur batteries with high sulfur loadings

Abstract

The commercialization of lithium-sulfur batteries (LSBs) faces challenges such as low sulfur loading and limited utilization. This paper addresses these challenges by designing furfuryl alcohol (FA)-derived and recyclable nano-ZnO-templated hierarchical porous carbons (HPCs) as cathode materials. FA not only acts as a precursor for carbon but also serves as a solvent, offering advantages in terms of simultaneous nitrogen doping, transition metal loading and HPC formation. Nano-ZnO with different sizes and shapes is used as a hard template to create tunable and interconnected mesopores in the HPCs.ZnO is chosen due to its low cost, ease of preparation, as well as its ability to be cyclically utilized. The resulting HPCs, including those doped with nitrogen (N-doped HPC or HPNC) and modified with heteronuclear single-atoms, feature a tunable pore structure, which increases pore volume and specific surface area. This leads to much enhanced sulfur loading capacity, improved battery stability, and better rate performance. The benefits of the HPC cathodes were verified in LSBs with an ultra-high S loading of 12.4 mg cm^-2 and a low electrolyte/S ratio of 4.0 μL mg^-1. Furthermore, the HPC or HPNC modified with nickel-cobalt dual-atom sites effectively catalyzes the conversion of polysulfides. These HPC cathodes enable LSBs to achieve a reversible capacity of 902.8 mA h g^-1 with a capacity retention of 74.0% after 500 cycles at 1 C.