Sulfur cathodes in conversion reaction batteries offer high gravimetric capacity but suffer from parasitic polysulfide shuttling. We demonstrate here that transition metal chalcogels of approximate formula MoS 3.4 achieve high gravimetric capacity close to 600 mAh g −1 (close to 1000 mAh g −1 on a sulfur-basis), as electrode materials for lithium-ion batteries. Transition metal chalcogels are amorphous, and comprise polysulfide chains connected by inorganic linkers. The linkers appear to act as a "glue" in the electrode to prevent polysulfide shuttling. The Mo chalcogels function as electrodes in carbonate-as well as ether-based electrolytes, which further provides evidence for polysulfide solubility not being a limiting issue. We employ X-ray spectroscopy and operando pair distribution function techniques to elucidate the structural evolution of the electrode. Raman and X-ray photoelectron spectroscopy track the chemical moieties that arise during the anion-redox-driven processes. We find the redox state of Mo remains unchanged across the electrochemical cycling and correspondingly, the redox

The stability of W, Mo, and Ta in contact with single-crystal β-SiC at elevated temperatures has been investigated using Auger sputter profiling. All three metals were found to form a thin-mixed layer of metal carbide and silicide upon metal deposition at room temperature. This layer is thought to be the result of surface defects which weaken the Si—C bonds and allow a low-temperature reaction to occur. Upon heating, the Ta readily reacts with the SiC substrate and forms a mixed layer of Ta carbide and silicide at annealing temperatures as low as 400 °C, however, the W/SiC and Mo/SiC systems are stable and change very little after annealing at 850 and 800 °C, respectively.

Transition metal phosphorus trisulfide materials have received considerable research interest since the 1980–1990s as they exhibit promising energy conversion and storage properties. However, the mechanistic insights into Li-ion storage in these materials are poorly understood to date. Here, we explore the lithiation of NiPS3 material by employing in situ pair-distribution function analysis, Monte Carlo molecular dynamics calculations, and a series of ex situ characterizations. Our findings elucidate complex ion insertion and storage dynamics around a layered polyanionic compound, which undergoes intercalation and conversion reactions in a sequential manner. This study of NiPS3 material exemplifies the Li-ion storage mechanism in transition metal phosphorus sulfide materials and provides insights into the challenges associated with achieving reliable, high-energy phosphorus trisulfide systems.

Many of the promising, high-performing solid electrolytes for lithium-ion batteries are amorphous or contain an amorphous component, particularly in the Li thiophosphate Li 2 S-P 2 S 5 compositional series (LPS). An explicit study of the local structure in four samples of ostensibly identically-prepared 70Li 2 S-30P 2 S 5 glass reveals substantial variation in the ratio between the two main local structural units in this system: PS 4 3− tetrahedra and P 2 S 7 4− corner-sharing tetrahedral pairs. Local structural and compositional probes including Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray pair distribution analysis are employed here to arrive at a consistent description of the relative amounts of isolated tetrahedral units, which vary by 13% across the samples measured. This local structure variation translates to differences in the activation energies measured by electrochemical impedance spectroscopy in these samples, such that the higher concentration of isolated tetrahedra corresponds to a lower activation energy. The measured temperature-dependent ionic conductivity data are compared to conductivity results across the literature reported on the same compositions, highlighting the variation in measured activation energy for nominally identical samples.These findings have implications for the critical need to play close attention to the local structure in solid electrolytes, particularly in systems that are glasses, glass-ceramics, or even comprise a small amorphous contribution.

Abstract