Synergistic mediation of sulfur conversion in lithium–sulfur batteries by a Gerber tree-like interlayer with multiple components

Abstract

Although the composite of metal oxide and porous carbon has been confirmed as an effective material to chemically adsorb polysulfides, the low conductivity of the metal oxide results in the need for extra pathways for the diffusion of polysulfides from adsorption sites to redox-active sites. This process results in sluggish reaction kinetics and escaped polysulfides. In this work, a Gerber tree-like interlayer with multiple components was designed to fully mediate the electrochemical conversion of Li–S batteries and shorten the diffusion distance of polysulfides in the composite. The branches of the interlayer contained TiO₂ and Co₃O₄ nanocrystals embedded into N-doped porous carbon, while the fruit was catalytic metal cobalt. The two co-existing chemical adsorbents ensure the restriction of polysulfides through S–Ti–O bonding and Lewis acid–base interaction. Moreover, the metal Co catalyzes the transformation of adsorbed polysulfides into low-order ones, which largely shortens the diffusion pathway, improving the reaction kinetics and preventing the migration of polysulfides. The cell with the interlayer exhibited outstanding electrochemical performance. After 100 cycles, a reversible capacity of 968 mA h g⁻¹ was maintained at 0.1C with a stable capacity retention of 85%. Even at the current rate of 1C, the cell delivered a capacity of 684.5 mA h g⁻¹ after 300 cycles.