Electrocatalysts work better in lean-electrolyte lithium-sulfur batteries

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 a titanium nitride (TiN) electrocatalyst. Similarly, the discharge capacity increment and cell polarization decrease afforded by the TiN electrocatalyst are more significant in lean-electrolyte Li-S batteries than in 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 the TiN electrocatalyst. This work elucidates that electrocatalysts are more effective in lean-electrolyte Li-S batteries and highlights advanced electrocatalyst design for high-energy-density Li-S batteries. The cathode kinetics promotion effectiveness of electrocatalysts is evaluated in lean-electrolyte lithium-sulfur batteries. The improvement of polysulfide conversion kinetics and battery performance is more significant at higher sulfur concentration.