Development of a High Energy Density, Long Cycle Life and Safety Enhanced Li-S Battery

摘要

Rechargeable lithium-sulfur (Li-S) batteries are widely considered the most promising "Beyond Li-ion" candidates, notably for their high theoretical energy density. The low and moderate atomic weight of Li and S, respectively, translates to a battery chemistry pairing that is lightweight. Since each S atom can ultimately host two lithium ions (Li~+), compared with 0.5-0.7 Li~+ per host atom in Li-ion batteries, the Li-S battery chemistry offers a much higher Li storage capacity potential. Assuming a complete redox couple reaction, S_8 + 16Li~+ + 16e~- ←→ 8Li_2S, the S cathode can have a high theoretical specific capacity of 1672 mAh/g with an average discharge voltage of ～2.1 V (vs. Li/Li~+), which leads to a theoretical specific energy of -2500 Wh/kg based on the active material weight of a Li-S cell. Other compelling attributes of Li-S batteries include high S natural abundance, low cost of S materials and safety characteristics owing to an intrinsic tolerance to overcharge. In addition, the primary constituents of Li-S batteries are non-toxic and environmentally friendly.