The Failure Mechanism of Lithium-Sulfur Batteries under Lean-Ether-Electrolyte Conditions

With a superb ability to dissolve the long-chain lithium polysulfides (Li2S4-8, LPSs) intermediates and promote the conversion between sulfur (S) and lithium sulfide (Li2S), ether-based electrolytes have been widely employed in lithium-sulfur (Li-S) batteries. While for ether-based Li-S batteries, the low reaction barrier is only overserved under superfluous electrolyte conditions. Aiming to figure out how Li-S batteries work and fail under lean-ether electrolyte conditions, herein, we carefully simulated the internal electrolyte environment and investigated the electrochemical behavior of the ether-based Li-S batteries under the different E/S ratios (1, 2, 3, 4, 6, and 10 mu L mg(-1)). The physicochemical and electrochemical characterizations reveal that the dissolution of the long-chain LPSs intermediates in lean ether electrolytes significantly reduces the wettability and conductivity of the electrolytes, and consequently results in the increased internal contact and charge-transfer resistance of the cells, which are responsible for the failure of the Li-S batteries under lean-ether-electrolyte conditions. We also demonstrate that by replacing the ether electrolytes with a sparingly solvating electrolyte, the electrochemical performance of the lean-electrolyte Li-S batteries could be markedly improved, which directs the future development of the high-energy Li-S batteries.