Open-Framework Chalcogenide (H₃O)KCu₆Ge₂S₈·nH₂O Exhibiting High Mixed Proton–Electron Conduction

Abstract

Mixed ion−electron conductors have a wide range of important applications in devices relying on mixed ion−electron transport, mainly including conducting polymer composites and ceramics. Herein, we present a new type of mixed ion−electron conductor, an open-framework chalcogenide, (H 3 O)KCu 6 Ge 2 S 8 •nH 2 O (1), with a three-dimensional (3D) framework and two types of one-dimensional (1D) channels, occupied by hydronium ions and potassium ions, respectively. Thermogravimetric (TG) and powder X-ray diffraction (PXRD) measurements suggest that the hydrated proton species in the channels of 1 are in the form of H 2n+1 O n + (n > 1). The impedance measurements reveal that 1 is an intrinsic mixed proton− electron conductor. In the N 2 atmosphere, the conductivity (σ) of 1 increases with release of water molecules and increasing temperature with σ = 0.71 S cm −1 at 123 K and 1.61 S cm −1 at 473 K in the first cooling run, and in this case, the electron conduction is much higher than the ion conduction. At 98% relative humidity (RH), however, the situation is opposite, and the proton conductivity of 1 is higher than its electron conduction with an ion conductivity (σ i )/electron conductivity (σ e ), σ i /σ e , of 1.99 × 10 −3 /6.31 × 10 −4 S cm −1 at 298 K and 2.49 × 10 −2 /2.52 × 10 −3 S cm −1 at 343 K. To the best of our knowledge, 1 is the first example of an open-framework material with mixed proton−electron conduction, and this study demonstrates that open-framework materials, including chalcogenides, MOFs, and COFs, are good candidates for mixed proton− electron conductors.

Interdigitated cathode–electrolyte architectural design for fast-charging lithium metal battery with lithium oxyhalide solid-state electrolyte

“…The formation of this solid-state impurity 63 can be explained by the interaction between protonated water cations, oxygen, and chloride anions, similar to the mechanism described for sulfur-containing hydronium-based compounds. 64,65 On the contrary, the XRD spectra of the S-1 and S-2 samples (Fig. 2(a) and (b)) match the simulated XRD data (Fig.…”

Decavanadate-Type Polyoxometalate Anions Encapsulated in a MIL-100 Framework with Enhanced Mixed Ion–Electron Conduction and Potential Application as Cathode Materials for a Lithium Ion Battery

“…The measurements of chronoamperometry were performed at the selected temperatures for MIL-100 and NaMoV@MIL-100-3, and the plots of current vs time are provided in Figure a,b. The current drops rapidly during the first 150 s and then gradually stabilizes at a constant value over time, unveiling that MIL-100 and NaMoV@MIL-100-3 have both ion and electron conduction . NaMoV@MIL-100-3 is, to the best of our knowledge, the first example of a POM@MOF material with mixed ion–electron conduction.…”

“…The current drops rapidly during the first 150 s and then gradually stabilizes at a constant value over time, unveiling that MIL-100 and NaMoV@MIL-100-3 have both ion and electron conduction. 31 NaMoV@MIL-100-3 is, to the best of our knowledge, the first example of a POM@MOF material with mixed ion−electron conduction. Ion conduction is responsible for the sudden drop in current within the first 150 s, and electron conduction is responsible for the portion of steady current.…”

Mixed-Dimensional (2D/3D/3D) Heterostructured Vanadium Oxide with Rich Oxygen Vacancies for Aqueous Zinc Ion Batteries with High Capacity and Long Cycling Life

“…The nearly frequencyindependent behavior of σ suggests exclusive electronic conduction in both VO x and V 2 O 5 . 25 Notably, at 273 K, σ measured 4.5 × 10 −3 S cm −1 for VO x , increasing to 1.1 × 10 −2 S cm −1 at 313 K, and further escalating to 0.20 S cm −1 at 493 K, demonstrating the exceptional electronic conductivity of VO x . Conversely, V 2 O 5 exhibited notably lower electrical conductivity (approximately 2 orders of magnitude) than VO x at equivalent temperatures.…”

“…Figure a,b depicts σ plotted against the frequency for selected temperatures corresponding to VO x and V 2 O 5 . The nearly frequency-independent behavior of σ suggests exclusive electronic conduction in both VO x and V 2 O 5 . Notably, at 273 K, σ measured 4.5 × 10 –3 S cm –1 for VO x , increasing to 1.1 × 10 –2 S cm –1 at 313 K, and further escalating to 0.20 S cm –1 at 493 K, demonstrating the exceptional electronic conductivity of VO x .…”