Solid-state batteries represent a promising advance in battery technology for meeting the expected growing demand for higher energy and power density of batteries, which are essential for an efficient electromobility. Within this battery concept, the conventionally liquid electrolyte in lithium-ion-batteries is replaced by a solid layer. For this purpose, sulfide-based electrolytes exhibit exceptional ionic conductivities and are therefore considered a suitable material. However, the high chemical reactivity of sulfides poses a key challenge, especially when exposed to ambient atmospheres. Toxic hydrogen sulfide (H2S) forms and the materials degrade when exposed even to small amounts of humidity within the ambient atmosphere, thus having a detrimental effect on battery performance.
Controlling sulfide reactivity in battery cell manufacturing requires specific and cost-effective conditioning of the process atmosphere. In the present research, the formation of hydrogen sulfide in sulfidic solid electrolytes under different production atmospheres is investigated. Using an innovative experimental setup, sulfide separator samples are exposed to defined ambient conditions, which simulate dynamic air fluctuations comparable to laboratory-scale dry room conditions. The results show significant H2S formation at dew points above -40 °C in atmospheres with constant air circulation. Irreversible morphological material changes observed by microscopic imaging underline the relevance of precise investigations under real and controllable conditions.
The research concludes with recommendations for an economically suitable and material-adapted atmosphere for the production of solid-state batteries, taking into account the scaling of production in a dry room environment at the Battery LabFactory Braunschweig. Thus, the innovative experimental setup enables further investigations into a safe and more cost-efficient design of process atmospheres, which contributes to a future scalable production with sulfide-based solid electrolytes.