According to research the Lithium Sulphides have a possible energy density of 4 times Lithium Polymer but the problem seems to be cycle life...whilst 200 plus kms would be a wonderful range but not at the cost of maybe only 40-50 cycles,perhaps only 2 months usage.
Quote...By combining the new cathode with the previously developed silicon anode, the team created a battery with an initial discharge of 630 watt-hours per kilogram of active ingredients. This represents an approximately 80 percent increase in the energy density over commercially available lithium-ion batteries, according to Stanford's Cui, who was a coauthor of a paper describing the work published last month in Nano Letters. Further increases in energy density--as much as four times that of lithium-ion batteries--are theoretically achievable by optimizing the battery's electrodes, Cui says.
The new battery still has significant issues, particularly in maintaining capacity. After just five discharge and recharge cycles, the cells lost one-third of their initial energy storage capacity and ceased to function after 40 to 50 cycles. The loss is likely due to polysulfides, chemicals that form during normal discharging and recharging. If allowed to dissolve into the battery's liquid electrolyte, polysulfides can poison the battery by blocking future charging and discharging. "This is a huge issue," Cui says. "We are making some great progress, but we certainly aren't there yet to compete with current technology in terms of cycle life."
