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The layered transition metal chalcogenides MCrX2 (M = Ag, Cu; X = S, Se, Te) are of interest for energy storage because chemically Li-substituted analogs were reported as superionic Li+ conductors. The coexistence of fast ion transport and reducible transition metal and chalcogen elements suggests that this family may offer multifunctional capability for electrochemical storage. Here, we investigate the electrochemical reduction of AgCrSe2 and CuCrSe2 in non-aqueous Li- and Na-ion electrolytes using electrochemical measurements coupled with ex situ characterization (scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy). Both compounds delivered high initial specific capacities (~ 560 mAh/g), corresponding to 6.64 and 5.73 Li+/e- per formula unit for AgCrSe2 and CuCrSe2, respectively. We attribute this difference to distinct reduction pathways: 1) Li+ intercalation to form LiCrSe2 and extruded Ag or Cu, 2) conversion of LiCrSe2 to Li2Se, and 3) formation of an Ag-Li alloy at the lowest potential, operative only in AgCrSe2. Consistent with this proposed mechanism, step 3 was absent during reduction of AgCrSe2 in a Na-ion electrolyte since Ag does not alloy with Na. These results demonstrate the complex reduction chemistry of MCrX2 in the presence of alkali ions, providing insights into the use of MCrX2 materials as alkali ion superionic conductors or high capacity electrodes for lithium or sodium-ion type batteries.
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MoS 2 Passivated Multilayer Graphene Membranes for Li‐Ion Extraction From Seawater
Abstract Abundant Li resources in the ocean are promising alternatives to refining ore, whose supplies are limited by the total amount and geopolitical imbalance of reserves in Earth's crust. Despite advances in Li+extraction using porous membranes, they require screening other cations on a large scale due to the lack in precise control of pore size and inborn defects. Herein, MoS2nanoflakes on a multilayer graphene membrane (MFs‐on‐MGM) that possess ion channels comprising i) van der Waals interlayer gaps for optimal Li+extraction and ii) negatively charged vertical inlets for cation attraction, are reported. Ion transport measurements across the membrane reveal ≈6‐ and 13‐fold higher selectivity for Li+compared to Na+and Mg2+, respectively. Furthermore, continuous, stable Li+extraction from seawater is demonstrated by integrating the membrane into a H2and Cl2evolution system, enabling more than 104‐fold decrease in the Na+concentration and near‐complete elimination of other cations.
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- PAR ID:
- 10411059
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Small
- Volume:
- 19
- Issue:
- 18
- ISSN:
- 1613-6810
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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