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Abstract Lithium‐rich transition metal chalcogenides are witnessing a revival as candidates for Li‐ion cathode materials, spurred by the boost in their capacities from transcending conventional redox processes based on cationic states and tapping into additional chalcogenide states. A particularly striking case is Li₂TiS_3‐ySe_y, which features a d⁰metal. While the end members are expectedly inactive, substantial capacities are measured when both Se and S are present. Using X‐ray absorption spectroscopy, it is shown that the electronic structure of Li₂TiS_3‐ySe_yis not a simple combination of the end members. The data confirm previous hypotheses that, in Li₂TiS_2.4Se_0.6, this behavior is underpinned by concurrent and reversible redox of only S and Se, and identify key electronic states. Moreover, wavelet transforms of the extended X‐ray absorption fine structure provide direct evidence of the formation of short Se–Se units upon charging. The study uncovers the underpinnings of this intriguing reactivity and highlights the richness of redox chemistry in complex solids. 

Abstract High‐efficiency and low‐cost catalysts for oxygen evolution reaction (OER) are critical for electrochemical water splitting to generate hydrogen, which is a clean fuel for sustainable energy conversion and storage. Among the emerging OER catalysts, transition metal dichalcogenides have exhibited superior activity compared to commercial standards such as RuO₂, but inferior stability due to uncontrolled restructuring with OER. In this study, we create bimetallic sulfide catalysts by adapting the atomic ratio of Ni and Co in Co_xNi_1‐xS_yelectrocatalysts to investigate the intricate restructuring processes. Surface‐sensitive X‐ray photoelectron spectroscopy and bulk‐sensitive X‐ray absorption spectroscopy confirmed the favorable restructuring of transition metal sulfide material following OER processes. Our results indicate that a small amount of Ni substitution can reshape the Co local electronic structure, which regulates the restructuring process to optimize the balance between OER activity and stability. This work represents a significant advancement in the development of efficient and noble metal‐free OER electrocatalysts through a doping‐regulated restructuring approach. 

Abstract Electrode stabilization by surface passivation has been explored as the most crucial step to develop long‐cycle lithium‐ion batteries (LIBs). In this work, functionally graded materials consisting of “conversion‐type” iron‐doped nickel oxyfluoride (NiFeOF) cathode covered with a homologous passivation layer (HPL) are rationally designed for long‐cycle LIBs. The compact and fluorine‐rich HPL plays dual roles in suppressing the volume change of NiFeOF porous cathode and minimizing the dissolution of transition metals during LIBs cycling by forming a structure/composition gradient. The structure and composition of HPL reconstructs during lithiation/delithiation, buffering the volume change and trapping the dissolved transition metals. As a result, a high capacity of 175 mAh g⁻¹(equal to an outstanding volumetric capacity of 936 Ah L⁻¹) with a greatly reduced capacity decay rate of 0.012% per cycle for 1000 cycles is achieved, which is superior to the NiFeOF porous film without HPL and commercially available NiF₂‐FeF₃powders. The proposed chemical and structure reconstruction mechanism of HPL opens a new avenue for the novel materials development for long‐cycle LIBs.