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1. Electrochemical lithiation of the layered superionic conductors AgCrSe₂ and CuCrSe₂

   https://doi.org/10.26434/chemrxiv-2025-wg75n  

   Moon, Seongbak; Rahman, Md Towhidur; Holzapfel, Noah P; Zevalkink, Alexandra; Augustyn, Veronica (October 2025, ChemRxiv)

   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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2. Sodium and potassium ion storage in cation substituted 2D MoWSe ₂ : insights into the effects of upper voltage cut-off

   https://doi.org/10.1088/1361-6528/acdf66  

   Dey, Sonjoy; Singh, Gurpreet (July 2023, Nanotechnology)

   Abstract The superior properties, such as large interlayer spacing and the ability to host large alkali-metal ions, of two-dimensional (2D) materials based on transition metal di-chalcogenides (TMDs) enable next-generation battery development beyond lithium-ion rechargeable batteries. In addition, compelling but rarely inspected TMD alloys provide additional opportunities to tailor bandgap and enhance thermodynamic stability. This study explores the sodium-ion (Na-ion) and potassium-ion (K-ion) storage behavior of cation-substituted molybdenum tungsten diselenide (MoWSe₂), a TMD alloy. This research also investigates upper potential suspension to overcome obstacles commonly associated with TMD materials, such as capacity fading at high current rates, prolonged cycling conditions, and voltage polarization during conversion reaction. The voltage cut-off was restricted to 1.5 V, 2.0 V, and 2.5 V to realize the material’s Na⁺and K⁺ion storage behavior. Three-dimensional (3D) surface plots of differential capacity analysis up to prolonged cycles revealed the convenience of voltage suspension as a viable method for structural preservation. Moreover, the cells with higher potential cut-off values conveyed improved cycling stability, higher and stable coulombic efficiency for Na⁺and K⁺ion half-cells, and increased capacity retention for Na⁺ion half-cells, respectively, with half-cells cycled at higher voltage ranges. 

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3. Recent advances in the stabilization of monomeric stibinidene chalcogenides and stibine chalcogenides

   https://doi.org/10.1039/d4dt00506f  

   Wenger, John S; Johnstone, Timothy C (May 2024, Dalton Transactions)

   The synthetic strategies employed to isolate monomeric stibinidene chalcogenides (RSbCh) and monomeric stibine chalcogenides (R₃SbCh) are discussed, and a perspective on the outcomes and future directions of this exciting area is provided. 

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4. Solution‐Processed Arsenic Chalcogenides as Dopant Source and Back Contact for Efficient CdSeTe Solar Cells

   https://doi.org/10.1002/solr.202500229  

   Duan, Xiaomeng; Wang, Yizhao; Li, Lin; Yan, Feng (May 2025, Solar RRL)

   Group V doping in CdSeTe device can improve power conversion efficiency (PCE) and device stability. Arsenic (As) incorporation into CdSeTe has been demonstrated via both in situ and ex situ techniques; however, optimizing the back contact for group V‐doped CdSeTe devices remains a critical challenge. Here, solution‐processed arsenic chalcogenides (i.e., As₂Te₃and As₂Se₃) as dual‐role materials, serving as both dopants and back‐contact materials for high‐efficiency CdSeTe devices, are investigated. During the formation of the back contact, a portion of the arsenic chalcogenides diffuses into the CdSeTe absorber, facilitating p‐type doping. The remaining materials forms a stable back‐contact layer that facilitate carrier collection and reducing recombination losses at the CdSeTe back surface. Particularly, CdSeTe device employing Te rich As₂Te₃layer as the dopant and back‐contact materials achieves a PCE of 18.34%, demonstrating the dual functionality of solution‐processed arsenic chalcogenides in simultaneously doping the absorber and optimizing charge extraction. This solution based cost‐effective As doping approach offers a promising pathway for advancing CdSeTe photovoltaic technology. 

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5. Studies of Functional Defects for Fast Na‐Ion Conduction in Na _{3− y} PS _{4− x} Cl _x with a Combined Experimental and Computational Approach

   https://doi.org/10.1002/adfm.201807951  

   Feng, Xuyong; Chien, Po‐Hsiu; Zhu, Zhuoying; Chu, Iek‐Heng; Wang, Pengbo; Immediato‐Scuotto, Marcello; Arabzadeh, Hesam; Ong, Shyue_Ping; Hu, Yan‐Yan (January 2019, Advanced Functional Materials)

   Abstract All‐solid‐state rechargeable sodium (Na)‐ion batteries are promising for inexpensive and high‐energy‐density large‐scale energy storage. In this contribution, new Na solid electrolytes, Na_3−yPS_4−xCl_x, are synthesized with a strategic approach, which allows maximum substitution of Cl for S (x= 0.2) without significant compromise of structural integrity or Na deficiency. A maximum conductivity of 1.96 mS cm⁻¹at 25 °C is achieved for Na_3.0PS_3.8Cl_0.2, which is two orders of magnitude higher compared with that of tetragonal Na₃PS₄(t‐Na₃PS₄). The activation energy (E_a) is determined to be 0.19 eV. Ab initio molecular dynamics simulations shed light on the merit of maximizing Cl‐doping while maintaining low Na deficiency in enhanced Na‐ion conduction. Solid‐state nuclear magnetic resonance (NMR) characterizations confirm the successful substitution of Cl for S and the resulting change of P oxidation state from 5+ to 4+, which is also verified by spin moment analysis. Ion transport pathways are determined with a tracer‐exchange NMR method. The functional detects that promote Na ‐ion transport are maximized for further improvement in ionic conductivity. Full‐cell performance is demonstrated using Na/Na_3.0PS_3.8Cl_0.2/Na₃V₂(PO₄)₃with a reversible capacity of ≈100 mAh g^‐1at room temperature. 

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