Growing sulfur batteries from crystals

Strain on demand for critical battery metals is forcing manufacturers to seek alternative materials. Sulfur’s high thermal stability and abundance are making it a promising emerging battery material. A new class of solid-state lithium-sulfur batteries developed by Theion GmbH (Berlin, Germany; www.theion.de) are produced using similar principles to semiconductor manufacturing in a proprietary, direct crystal imprinting/implanting (DCi) technology that drastically reduces the cost and energy required for producing batteries when compared to typical lithium-ion batteries (LIBs).

For its lithium-sulfur cathode technology, Theion is growing poly-crystalline sulfur wafers with hierarchical porosity down to 15% directly from molten sulfur using carbon-nanotube or graphene seed-crystal carriers. “We are applying a high-voltage electric field to induce growth of a sulfur wafer with tailored porosity by targeting the defect sites present on suitable seed carriers as nucleation points on which one-dimensional nano-sulfur is formed first. Then, as the process propagates along the seed carriers, crystal twinning and branching occurs,” explains Theion chief technology officer Marek Slavik.Theion’s DCi process enables the targeted addition of conductive paths to maximize active material and optimize energy content. Together, Theion says, these properties result in a battery with triple the range and usage time of traditional LIBs, with a 90% reduction in energy use to produce the batteries. The ability to use sulfur — an inexpensive industrial byproduct — to replace cobalt and nickel further lowers production costs.

“We are currently building a large wafer-growing system for 120-mm sulfur wafers at 15 mAh/cm². This is a fundamentally different production process than with typical LIBs, where everything starts as a slurry,” explains Slavik. By 2025, Theion expects to operate a gigawatt-scale production line. “The first adopters of the new batteries from the space industry are looking for high-energy options to deliver cargo into orbit,” adds Slavik.