Janus architecture host electrode for mitigating lithium-ion polarization in high-energy-density Li–S full cells†

Abstract

High-energy-density Li–S full cells require thick host electrodes, which are particularly challenged by diffusion-limited Li-ion polarization. Our study introduces a heterogeneous Janus architecture that mitigates this polarization and achieves uniform charge/discharge reaction rates across the electrodes. Janus electrodes are fabricated by incorporating Mo₂C-coated carbon nanotubes (CNTs) or carbon fibers (CFs) with their uncoated counterparts for the cathode and anode, respectively. At the cathode, the Janus film suppresses the polysulfide shuttle by delaying polysulfide diffusion, even under ultra-high S loading of 10 mg cm⁻². At the anode, the film uniformly regulates significant Li plating/stripping within the anode substrate, even at an exceptionally high areal capacity of 20 mA h cm⁻² accompanying the S loading. Equipped with Janus films on both electrodes and operating under practical conditions with an electrolyte-to-sulfur (E/S) ratio of 4.4 μL mg⁻¹ and a negative-to-positive (N/P) ratio of 2, our Li–S full cell achieves an energy density of 6.3 mA h cm⁻². These findings underscore the critical role of macroscopic control of the host electrode in enhancing performance.