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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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This content will become publicly available on December 12, 2026
Intercalation‐Induced Phase Transitions in Ferroelectric α‐In 2 Se 3
Abstract Specific ions can be intercalated into functional materials using the electrolyte gating technique, which has been widely used to regulate channel conductance in transistors and develop low‐power neuromorphic devices. However, in these devices, fundamental exploration of ion intercalation‐induced structural phase transitions remains largely overlooked and rarely explored. Here, the lithium‐based electrolyte gating technique is used to probe the collective interactions between ions, lattices, and electrons in a van der Waals ferroelectric semiconductor α‐In2Se3. Using a polymer electrolyte as the lithium‐ion reservoir and α‐In2Se3as the channel material, the intercalated lithium concentration via a gate electric field is modulated. This manipulation drives a phase transition in α‐In2Se3from a ferroelectric semiconductor to a dirty metal and finally to a metal, accompanied by a structural transformation. Concurrently, with enhanced intercalation, the ferroelectric hysteresis window progressively narrows and eventually disappears, indicating the evolution from switchable to non‐switchable polarization. This study represents a promising platform for the artificial construction of correlated material systems, enabling a systematic investigation into the interaction of ferroelectricity and electronic conduction using ion intercalation.
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- Award ID(s):
- 2429995
- PAR ID:
- 10653299
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Advanced Science
- ISSN:
- 2198-3844
- Page Range / eLocation ID:
- e13712
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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