IDTechEx: Lithium-sulfur batteries set to become billion-dollar industry
20 April 2025
In a recent report, “ Lithium Metal Batteries 2025-2035: Technology, Players and Forecasts”, market analyst firm IDTechEx predicts that the lithium-sulfur market will exceed US$1.3 billion by 2035.
Lithium-sulfur batteries are batteries with lithium metal anodes and sulfur cathodes. They feature a high gravimetric energy density, although their volumetric energy density is limited due to the large amount of sulfur needed for the cathode. Lithium-sulfur has also been noted for potential cost reductions due to the abundance of sulfur, as well as enhanced safety due to the non-reactivity of sulfur. Lithium-sulfur is already seeing development across multiple continents and is expected to achieve mass production by 2033.
Cell structure comparison for lithium metal cells vs. incumbent graphite-anode cells. Source: IDTechEx
Lithium-sulfur has seen development efforts in the past. However, the chemistry has been limited as a result of an intrinsic degradation method: polysulfide shuttle.
Polysulfides of the form Li2Sx are produced in the cathode and shuttle into the electrolyte, effectively leaching active materials away. These polysulfides can also reach the anode and begin a cycle of their own redox reactions, which reduces the effective redox potential of the cell. Polysulfides can also form an insoluble layer of Li2S at the anode, preventing ion transport. The overall effect of polysulfide shuttle is to significantly reduce the coulombic efficiency of the cell, severely impacting battery lifetime.
Source: IDTechEx
Lithium metal dendrite formation is also an issue, though it tends to be less significant than polysulfide shuttle. Lithium dendrites form at the anode and leach into the electrolyte, irreversibly reacting such that the active material of the cell is reduced. In addition, during charging and discharging, the sulfur cathode experiences significant swelling—as much as 80% during discharging. This places considerable pressure on the architecture of the cathode and potentially reduces the contact conductivity of the cell overall through the formation and nucleation of cracks.
Polysulfide shuttle can be counteracted in several ways. The most obvious approach may be to use a solid electrolyte, as this prevents polysulfides from shuttling. However, this can lead to significantly reduced conductivity at the interface between electrolyte and cathode, as sulfur is already a poor conductor. Alternative liquid electrolytes are a more compelling option. Polysulfides are soluble in incumbent liquid electrolytes used in graphite-anode lithium-ion. However, there are other solutions in which polysulfides are not soluble, cyclic ethers, short-chain ethers and glycol ethers.
Alternatively, a separator layer/membrane may be used to prevent polysulfide shuttle. The chosen membrane must be selective, allowing lithium-ions to pass but not polysulfides.
Cathode expansion can be solved using alternative cathode structures, e.g. expansion-tolerant lattices or stronger binders. Alternative materials may allow for the development of single-material structures without binders, which significantly enhances the rigidity of the current collector. An example is sulfurized polyacrylonitrile or SPAN.
Lithium-sulfur’s higher specific energy but lower energy density make it particularly suitable for applications in aviation, defence and maritime, especially unmanned aerial vehicles (UAVs) or drones. However, the chemistry is expected to also see some deployment in electric vehicles, especially heavy-duty electric vehicles. IDTechEx predicts that by 2035, more than 14 GWh will be produced globally.
Posted on 20 April 2025 in Batteries, Forecasts, Li-Sulfur, Market Background
greencarcongress.com |
