Nitrogen-rich azoles as trifunctional electrolyte additives for high-performance lithium-sulfur battery

Rechargeable lithium-sulfur (Li-S) batteries are considered one of the most promising energy storage techniques owing to the high theoretical energy density. However, challenges still remain such as the shuttle effect of lithium polysulfides (LPSs) and the instability of lithium metal anode. Herein, we propose to use nitrogen-rich azoles, i.e., triazole (Ta) and tetrazole (Tta), as trifunctional electrolyte additives for Li-S batteries. The azoles afford strong lithiophilicity for the chemisorption of LPSs. The density functional theory and experimental analysis verify the presence of Li bonds between the azoles and LPSs. The azoles can also interact with lithium salt in the electrolyte, leading to increase ionic conductivity and lithium-ion transference number. Moreover, the azoles render particle-like lithium deposition on the lithium metal anode, leading to superlong cycling of a Li symmetric cell. The Li-S batteries with Ta and Tta exhibit the initial discharge capacity of 1425.5 and 1322.2 mAh g−1, respectively, at 0.2C rate, and promising cycling stability. They also enable enhanced cycling performance of a Li-organosulfide battery.