(Invited) Enhancing Performance and Moisture Resistance of Solid Electrolyte in Sulfide-Based All-Solid-State Batteries via Oxygen Integration
Authors: Park Yongsun , Shim Yoonsu , Lee Junki , Yuk jong Min , Lee Chan-Woo , Kanno Ryoji , Nam Sangcheol , Kwon Ohmin 
Published: December 2024

Issues related to explosions and energy density constraints are presented by lithium-ion batteries (LIBs) employing organic electrolytes.1 The pursuit of overcoming these challenges has brought all-solid-state batteries (ASSBs), representing the next generation of batteries, to prominence as a viable solution. The interest has been directed towards sulfide-based solid electrolytes (SEs), recognized as a crucial component in ASSBs due to their elevated ionic conductivity. Nevertheless, challenges are encountered, encompassing the generation of hazardous hydrogen sulfide (H2S) attributed to the sulfide electrolytes' diminished chemical stability in the presence of moisture, which results in the degradation of cells.2 This necessitates the production of batteries in an environment devoid of reactive elements, thus imposing a hurdle for mass production. To address this issue, two strategies have been delineated: i) the integration of metal oxides such as Fe2O3, ZnO, and zeolite for the sequestration of H2S produced through hydrolysis; ii) the enhancement of SE's stability through doping with Bi, Sn, and Sb in alignment with the theory of hard and soft acids and bases (HSAB), or through replacement with oxides like Li2O and P2O5. The suppression of H2S generation might contribute to prolonged degradation of cells, as it entails the capture of H2S, a breakdown product of SEs. In contrast, the reinforcement of SE structures via the integration of oxygen derivatives is posited to provide the benefit of precluding the generation of H2S while preserving cell efficiency. Despite the notable influence of oxygen inclusion, the elucidation of its impact, anchored in dependable cell functionality and underlying mechanisms, has yet to be fully clarified.3,4 Thus, delving into the comprehension of structural reinforcement mechanisms facilitated by oxygen substitution and their implications is deemed of considerable importance for addressing the intrinsic challenges in SEs.

In this study, a novel argyrodite composition incorporating a specified quantity of oxygen has been introduced to simultaneously augment its resistance to moisture and enhance its electrochemical performance without detracting from either attribute. The advantageous effects of oxygen substitution on structural reinforcement, resistance to moisture, and battery properties are delineated. The augmentation of the cathode/SE interface stability through oxygen substitution has been corroborated employing a high-capacity NCM811 (LiNi0.8Co0.1Mn0.1O2), and the decomposition behavior has been delineated through X-ray photoelectron spectroscopy (XPS). An evaluation and comparison of moisture stability have been conducted using transmission electron microscope-selected-area electron diffraction (TEM-SAED), and the sites of oxygen substitution have been meticulously identified utilizing Rietveld refinement and Raman spectroscopy. A mechanism positing the stabilization of the PS4 unit, pivotal for moisture resistance through oxygen-mediated structural evolution, is proposed. Furthermore, the significance of the SE in facilitating the commercial viability of sulfide-based ASSBs, accompanied by a substantial enhancement in battery performance, has been elucidated.

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