Toward Environmentally Friendly Lithium Sulfur Batteries: Probing the Role of Electrode Design in MoS2-Containing Li-S Batteries with a Green Electrolyte

While lithium sulfur batteries (Li-S) hold promise as future high energy density low cost energy storage systems, barriers to implementation include low sulfur loading, limited cycle life, and the use of toxic electrolyte solvents. A comprehensive study of Li-S cells in the environmentally benign di(propylene glycol) dimethyl ether (DPGDME)-based electrolyte, using as-prepared MoS2 nanosheets derived from a facile aqueous microwave synthesis as polysulfide trapping agents, is reported herein for the first time. Conventional coated foil electrodes and binder-free electrodes (BFEs) with various structures are systematically generated and tested to correlate electrode design with the resulting electrochemical behavior. Significantly improved Li-S electrochemistry is demonstrated through the synergy of MoS2 chemistry and binder-free electrode engineering. In the coating configuration, the MoS2-containing cell evinced better rate performance and more stable cyclability than the cell without MoS2. In comparison with the coating counterparts, the BFE cells exhibited excellent cycle stability and superior rate capability (10-fold capacities and energy density per electrode weight with 20% higher retention rate) despite 2X higher areal sulfur loading. The BFE cell improvement can be attributed to the synergistic effect of the i) interconnected macroporous structure of CNT interlayers, providing a conductive framework, and ii) the efficient polysulfide trapping by the MoS2 nanosheets.