Suppressing Shuttle Effect through Solvent Coordination and Nitrate Synergy Enables Stable Lithium-Sulfur Batteries

The shuttling of soluble polysulfide (PS) intermediates between the cathode and anode leads to rapid capacity fade and remains one of the foremost barriers to the commercialization of lucrative lithium-sulfur (Li-S) batteries. Previous electrolyte strategies have been constrained by a critical trade-off: weakly coordinating electrolytes and electrode architectures effectively suppressing the shuttle effect at the expense of reduced capacity. Typically, strongly coordinating electrolytes deliver higher sulfur utilization but intensify polysulfide migration and mostly rely on LiNO₃ additives for anode stability. In this study, a balanced electrolyte design is introduced using a binary solvent system comprising strongly coordinating tetrahydrofuran (THF) and weakly coordinating cyclopentyl methyl ether (CPME). A direct correlation is established between solvent coordination strength, polysulfide solubility, and LiNO₃ concentration along with their combined influence on the shuttle effect. By tuning solvent polarity (dielectric constant) within the THF:CPME binary system, sufficient polysulfide dissolution is achieved to sustain robust redox kinetics while avoiding excessive dissolution that accelerates capacity decay. Using 0.7 M LiNO₃ in 4:1 THF:CPME electrolyte, the system delivers 92% capacity retention over 100 cycles, a ∼20% improvement over the conventional electrolyte, along with high Coulombic efficiency (99-100%). Further analysis confirms the formation of a LiNO₃-derived protective interphase and regulated polysulfide dissolution on both the anode and cathode surfaces.