Micro-Macroscopic Coupled Electrode Architecture for High-Energy-Density Lithium-Sulfur Batteries

Abstract

Practical implementation of lithium-sulfur (Li-S) batteries has been hindered by the difficulty of achieving satisfactory energy densities in a facile and sustainable way. The most widely adopted strategy aimed for improved energy density has been tailoring the microscopic structure of sulfur cathode materials to address fundamental challenges, which is, however, inadequate for the stabilization of the macroscopic cathode structure. Here, we propose a micro-macroscopic coupled electrode architecture comprising commercially available carbon nanotubes through a simple self-assembly and freeze-casting method. The microscopic structure of carbon nanotubes enables homogeneous accommodation of sulfur, and the self-assembled macroscopic interconnected framework provides abundant and interconnected channels for boosted transport of both electrons and lithium ions and well-localized polysulfide intermediates. With the use of the same carbon nanotube material, the micro-macroscopic coupled electrode shows obviously enhanced electrochemical performance in terms of high capacity and long cycle life as well as high sulfur loading, compared to a conventionally prepared electrode. This work sheds light on an avenue for achieving high-performance sulfur cathodes by demonstrating the effectiveness of macroscopic electrode design beyond complex design of microscopic material structures, which may be applicable in other battery systems.