Gas Evolution Analysis of Sulfide-Based All-Solid-State Li-Ion Battery

Sulfide-based all-solid-state Li-ion batteries employing Ni-rich cathodes have emerged as the most promising candidate for high specific capacity and excellent safety. Nevertheless, the unstable solid-solid interface between sulfide electrolytes and Ni-rich cathodes induces detrimental side reactions, which are primarily responsible for rapid capacity fading and even pose significant safety risks. Herein, in situ mass spectrometry is employed to systematically investigate the gas evolution throughout the electrochemical processes and thermal runaway scenarios. The electrolytes' intrinsic stability, operational temperature, and cell fabrication parameters have been studied in depth on how to influence solid-solid interfacial degradation mechanisms. The analysis of experimental results reveals dominant gaseous byproducts including H₂S, O₂, CO₂, and SO₂ during electrochemical operation. Thermal runaway conditions additionally generate sulfur allotropes, which challenges the conventional assumption of absolute safety in sulfide-based systems. This work provides crucial evaluation methods for developing safer high-specific-energy batteries by guiding the rational design of high-performance electrolyte and cathode materials.