First the use of sulfur instead of a less energy dense and more expensive substances such as cobalt and/or iron compounds found in lithium-ion batteries.

Issues that have slowed acceptance include the polysulfide "shuttle" effect that is responsible for the progressive leakage of active material from the cathode, resulting in too few recharge cycles.

[10] By 2023, Zeta Energy a Texas-based startup announced that multiple national laboratories had independently verified that its lithium-sulfur batteries based on sulfurized-carbon cathodes were polysulfide shuttle free.

[11] The competitive advantages of sulfurized-carbon cathodes (e.g., sulfurized polyacrylonitrile, also known as SPAN) were highlighted by a quantitative analysis performed by researchers at University of Maryland, College Park and Pacific Northwest National Laboratory in 2024.

[12] Their polysulfide shuttle free feature facilitates proper operation under lean electrolyte conditions (< 3 g·(A·h)−1), which was proved to be extremely crucial to attain the full potential of Li-S batteries.

The researchers proposed and analyzed unconventional perspectives on how to further improve both energy density and cycle life, highlighting the importance of a proper electrolyte (i.e., stable, lightweight, and highly Li+-conductive).

[13][14] A few years later the technology was improved by the introduction of organic solvents as PC, DMSO and DMF yielding a 2.35–2.5 V battery.

[21] Also that year, researchers employed aramid nanofibers (nanoscale Kevlar fibers), fashioned into cell membrane-like networks.

It addressed polysulfide shuttle by using ion selectivity, by integrating tiny channels into the network and adding an electrical charge.

The semi-reaction is therefore expressed as: Actually the sulfur reduction reaction to lithium sulphide is much more complex and involves the formation of lithium polysulphides (Li2Sx, 2 ≤ x ≤ 8) at decreasing chain length according to:[28] Over all: And the final step: The final product is actually a mixture of Li2S2 and Li2S rather than pure Li2S, due to the slow reduction kinetics at Li2S.

Carbon nanofibers provide an effective electron conduction path and structural integrity, at the disadvantage of higher cost.

[42] Moreover, the "shuttle" effect is responsible for the characteristic self-discharge of Li–S batteries, because of slow dissolution of polysulfide, which occurs also in rest state.

where ks, qup, [Stot] and Ic are respectively the kinetic constant, specific capacity contributing to the anodic plateau, the total sulfur concentration and charge current.

[44] Conventionally, Li–S batteries employ a liquid organic electrolyte, contained in the pores of PP separator.

[40] The electrolyte plays a key role in Li–S batteries, acting both on "shuttle" effect by the polysulfide dissolution and the SEI stabilization at anode surface.

[46] Long-chain polysulfides undergo nucleophilic attack on electrophilic sites of carbonates, resulting in the irreversible formation of by-products as ethanol, methanol, ethylene glycol and thiocarbonates.

[10] One of the primary factors limiting the lifespan of Li-S batteries is the dissolution of polysulfides in the electrolyte, which leads to the shuttle effect and results in capacity loss over time.

[50] The operating temperature and cycling rate also play significant roles in determining the lifespan of Li-S batteries.

Companies such as Sion Power have partnered with Airbus Defence and Space to test their lithium sulfur battery technology.

Airbus Defense and Space successfully launched their prototype High Altitude Pseudo-Satellite (HAPS) aircraft powered by solar energy during the day and by lithium sulfur batteries at night in real life conditions during an 11-day flight.

[86] Monash University's Department of Mechanical and Aerospace Engineering in Melbourne, Australia developed an ultra-high capacity Li–S battery that has been manufactured by partners at the Fraunhofer Institute for Material and Beam Technology in Germany.

[89] In June 2023, San Jose, California company Lyten started up a pilot production line making about 100 batteries a day.

[90] In 2024, Lyten announced plans a billion-dollar gigafactory in Reno, Nevada, to build up to 10 gigawatt-hours of lithium–sulfur batteries annually.