Design of Non-Depleting Electrolyte Additive to Prolong the Cycle Life of Practical Lithium-Sulfur Batteries

Battery technology is pivotal in addressing energy efficiency and environmental sustainability challenges. Lithium-sulfur (Li-S) batteries feature promising high energy density and sustainability, but are hindered by a short cycle life under lean lithium and electrolyte conditions. A critical hurdle for Li-S batteries is the selection of an optimal electrolyte solution, crucial for controlling effective polysulfide electrochemical reactions. The conventional ether- based Li-S electrolyte, consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium nitrate (LiNO3), frequently suffers from LiNO3 depletion in high-energy-density applications. To address the capacity decay in Li-S batteries caused by LiNO3 depletion, this investigation introduces 2-nitrophenol lithium (NPL) as an alternative. By incorporating 25 1 mM NPL and 1 M LiTFSI in a 1,3-dioxolane/1,2-dimethoxyethane (DOL/DME) solvent, NPL mediates polysulfide oxidation during charging and prevents polysulfide corrosion, therefore improving Li retention and plating behavior. This results in Li-S batteries with NPL achieving 310 cycles, significantly surpassing the 75 cycles observed with traditional LiNO3-containing electrolytes using lean lithium anode. Pouch cells incorporating NPL exhibit stable cycling over 80 cycles, maintaining 75% of their capacity. The molecular structure of NPL prevents decomposition and facilitates interaction with polysulfides to minimize corrosion, positioning it as a strong substitute for LiNO3. This highlights NPL as a promising solution for extending the lifespan of Li-S batteries.