Electrocatalysts work better in lean-electrolyte lithium‒sulfur batteries

Abstract

Reducing electrolyte usage constitutes the prerequisite to construct high-energy-density lithium‒sulfur (Li‒S) batteries. However, the cathode kinetics is severely blocked under lean-electrolyte conditions. Electrocatalysts have been widely employed to boost the cathode kinetics, yet their effectiveness under lean-electrolyte conditions remains unclear. Herein, the cathode kinetics promotion effectiveness of electrocatalysts is systematically evaluated in lean-electrolyte Li‒S batteries. The kinetics promotion effects on both liquid‒liquid and liquid‒solid conversions are more prominent at higher sulfur concentrations using the titanium nitride (TiN) electrocatalyst. Similarly, discharge capacity increment and cell polarization decrease afforded by the TiN electrocatalyst are more significant in lean-electrolyte Li‒S batteries than the flooded-electrolyte ones. Polarization decoupling analysis further identifies activation polarization as the main challenge under lean-electrolyte conditions, which can be effectively overcome by the TiN electrocatalyst. Moreover, the energy density of 2 Ah Li–S pouch cells increases by 19% using TiN electrocatalyst. This work elucidates electrocatalysts are more effective in lean-electrolyte Li–S batteries and highlights advanced electrocatalyst design for high-energy-density Li–S batteries.