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The ion insertion properties of MoS2 continue to be of widespread interest for energy storage. While much of the current work on MoS2 has been focused on the high capacity four-electron reduction reaction, this process is prone to poor reversibility. Traditional ion intercalation reactions are highlighted and it is demonstrated that ordered mesoporous thin films of MoS2 can be utilized as a pseudocapacitive energy storage material with a specific capacity of 173 mAh g−1 for Li-ions and 118 mAh g−1 for Na-ions at 1 mV s−1. Utilizing synchrotron grazing incidence X-ray diffraction techniques, fast electrochemical kinetics are correlated with the ordered porous structure and with an iso-oriented crystal structure. When Li-ions are utilized, the material can be charged and discharged in 20 seconds while still achieving a specific capacity of 140 mAh g−1. Moreover, the nanoscale architecture of mesoporous MoS2 retains this level of lithium capacity for 10 000 cycles. A detailed electrochemical kinetic analysis indicates that energy storage for both ions in MoS2 is due to a pseudocapacitive mechanism. [ABSTRACT FROM AUTHOR]

Vapor deposition techniques are particularly attractive for lithium-ion battery materials, for both powder coatings as well as thin-film electrodes. To increase capacity, alloying anodes represent a new class of materials for energy-dense films. Herein, we use metal organic chemical vapor deposition to prepare bismuth telluride (Bi 2 Te 3) and antimony telluride (Sb 2 Te 3) thin-film electrodes, materials which have not been studied extensively for lithium-ion batteries, and assess their lithium storage performance. A deposition process was developed to yield continuous thin films with thicknesses ranging from 0.5 to 1.4 μm on electrically conductive substrates. By varying the growth time of the deposition process, capacities up to ∼0.3 mA h cm−2 were obtained with a growth time of 60 min. The Sb 2 Te 3 thin-film electrode outperforms Bi 2 Te 3 for similar deposition conditions, which is primarily attributed to the high performance of native Sb that exhibits high capacity and stable cycling. Although the final phase of these thin-film electrodes separates into a biphasic domain, it is evident that the starting compound Sb 2 Te 3 is stable up to 50 cycles. Yet, since cracks are still observed from post-cycling scanning electron microscopy, it is evident that a proper balance between film thickness and cycling must be remediated. Image 1 • Metal organic chemical vapor deposition was used to prepare metal telluride thin-film electrodes. • Deposition times were optimized for the preparation of metal telluride thin-film electrodes. • Antimony telluride exhibited the highest electrochemical performance. • Post-cycled scanning electron microscopy showed cracking of the films after 50 charge/discharge cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • An electroanalytical method was used for tracking processes in Si anodes: 3D DRT. • This analysis allowed to identify the formation of two SEI time constants. • It was possible to observe that the time constant of Si lithiation becomes smaller upon cycling. An unconventional electroanalytical method has been used for tracking processes in silicon anodes in lithium ion batteries: a 3D visualization of relaxation times. Impedance data of the electrodes were collected at different potentials and different cycles during cyclic voltammetry, and were treated by means of the Distribution of Relaxation Times (DRT) method. A 3D visualization of the results allowed to identify the formation of a solid electrolyte interphase on the anode, composed of two layers with different relaxation times. Such findings are not possible by conventional analysis of impedance data by modeling with equivalent circuits, nor by simple DRT alone. Additionally, it was possible to observe that the characteristic relaxation time of the lithiation of the Si anode becomes smaller upon cycling, indicating that the material experiences structural transformations that allow it to lithiate faster. This result is relevant to motivate the use of micron-sized particles in the anode. [ABSTRACT FROM AUTHOR]