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  1. Free, publicly-accessible full text available October 1, 2024
  2. Abstract Developing efficient catalysts is of paramount importance to oxygen evolution, a sluggish anodic reaction that provides essential electrons and protons for various electrochemical processes, such as hydrogen generation. Here, we report that the oxygen evolution reaction (OER) can be efficiently catalyzed by cobalt tetrahedra, which are stabilized over the surface of a Swedenborgite-type YBCo 4 O 7 material. We reveal that the surface of YBaCo 4 O 7 possesses strong resilience towards structural amorphization during OER, which originates from its distinctive structural evolution toward electrochemical oxidation. The bulk of YBaCo 4 O 7 composes of corner-sharing only CoO 4 tetrahedra, which can flexibly alter their positions to accommodate the insertion of interstitial oxygen ions and mediate the stress during the electrochemical oxidation. The density functional theory calculations demonstrate that the OER is efficiently catalyzed by a binuclear active site of dual corner-shared cobalt tetrahedra, which have a coordination number switching between 3 and 4 during the reaction. We expect that the reported active structural motif of dual corner-shared cobalt tetrahedra in this study could enable further development of compounds for catalyzing the OER. 
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  3. Abstract

    The utilization of silicon anodes in all‐solid‐state lithium batteries provides good prospects for facilitating high energy density. However, the compatibility of sulfide solid‐state electrolytes (SEs) with Si and carbon is often questioned due to potential decomposition. Herein, operando X‐ray absorption near‐edge structure (XANES) spectroscopy, ex situ scanning electron microscopy (SEM), and ex situ X‐ray nanotomography (XnT) are utilized to investigate the chemistry and structure evolution of nano‐Si composite anodes. Results from XANES demonstrate a partial decomposition of SEs during the first lithiation stage, which is intensified by the presence of carbon. Nevertheless, the performances of first three cycles in Si–SE–C are stable, which proves that the generated media is ionically conductive. XnT and SEM results show that the addition of SEs and carbon improves the structural stability of the anode, with fewer pores and voids. A chemo‐elasto‐plastic model reveals that SEs and carbon buffer the volume expansion of Si, thus enhancing mechanical stability. The balance between the pros and cons of SEs and carbon in enhancing reaction kinetics and structural stability enables the Si composite anode to demonstrate the highest Si utilization with higher specific capacities and a better rate than pure Si and Si composite anodes with only SEs.

     
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  4. Abstract

    Due to its outstanding safety and high energy density, all‐solid‐state lithium‐sulfur batteries (ASLSBs) are considered as a potential future energy storage technology. The electrochemical reaction pathway in ASLSBs with inorganic solid‐state electrolytes is different from Li‐S batteries with liquid electrolytes, but the mechanism remains unclear. By combining operando Raman spectroscopy and ex situ X‐ray absorption spectroscopy, we investigated the reaction mechanism of sulfur (S8) in ASLSBs. Our results revealed that no Li2S8,Li2S6,and Li2S4were formed, yet Li2S2was detected. Furthermore, first‐principles structural calculations were employed to disclose the formation energy of solid state Li2Sn(1≤n≤8), in which Li2S2was a metastable phase, consistent with experimental observations. Meanwhile, partial S8and Li2S2remained at the full lithiation stage, suggesting incomplete reaction due to sluggish reaction kinetics in ASLSBs.

     
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  5. Abstract

    Due to its outstanding safety and high energy density, all‐solid‐state lithium‐sulfur batteries (ASLSBs) are considered as a potential future energy storage technology. The electrochemical reaction pathway in ASLSBs with inorganic solid‐state electrolytes is different from Li‐S batteries with liquid electrolytes, but the mechanism remains unclear. By combining operando Raman spectroscopy and ex situ X‐ray absorption spectroscopy, we investigated the reaction mechanism of sulfur (S8) in ASLSBs. Our results revealed that no Li2S8,Li2S6,and Li2S4were formed, yet Li2S2was detected. Furthermore, first‐principles structural calculations were employed to disclose the formation energy of solid state Li2Sn(1≤n≤8), in which Li2S2was a metastable phase, consistent with experimental observations. Meanwhile, partial S8and Li2S2remained at the full lithiation stage, suggesting incomplete reaction due to sluggish reaction kinetics in ASLSBs.

     
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