Herein, we report energy storage devices, which are based on densely packed, vertically aligned MoS2 (VA-MoS2) or planar oriented MoS2 (PO-MoS2) and compare their electrochemical performances. The VA-MoS2 films have been processed by chemical vapor deposition (CVD) to reach unprecedented micron-scale thick films while maintaining the vertical alignment for the whole thickness. The VA-MoS2 and the PO-MoS2 films form a high-performance Li-ion electrode, reaching the theoretical limits of reversible capacity for this material (800 mAh/g; twice the specific capacity of graphite). The vertical alignment allows faster charge-discharge rates while maintaining a high specific capacity (C-rate measurements). Noteworthy, the reversible cycling of the Li-ion electrode also benefits from the vertical alignment. In this article, we present the full synthesis, structural and electrochemical characterization of VA-MoS2 along with the properties of PO-MoS2 to deconvolute the intrinsic properties of MoS2 from the influence of the layers’ orientation.

In this manuscript, we report our investigation of anode materials for Li-ion batteries based on silicon-graphene oxide composites. Previous reports in the literature on silicon-graphene oxide (GO) composites as anodes have shown a large discrepancy between the electrochemical properties, mainly capacity and coulombic efficiency. In our research, the surface chemistry of Si nanoparticles has been functionalized to yield a chemical bond between the Si and GO, a further annealing step yields a Si-reduced GO (Si-rGO) composite while controlled experiments have been carried on mechanical mixing of GO and Si. For all samples, including a simple mixing of Si nanoparticles and GO, a high specific capacity of 2000 mA h g(Si)(-1) can be achieved for 50 cycles. The main difference between the samples can be observed in terms of coulombic efficiency, which will determine the future of these composites in full Li-ion cells. The Si-rGO composite shows a very low capacity fading and a coulombic efficiency above 99%. Furthermore, the Si-rGO composite can be cycled at very high rate to 20 C (charge in 3 minutes).

The efficient formulation of silicon based, highloading electrode with good capacity retention and cycling stability remains challenging. To gain a better understanding of the ongoing processes and failure mechanisms occurring during battery performance, operando micro-Raman spectroscopy is helpful to map the active silicon sites. Herein, we present the investigation of the electrochemical performance of anodes composed of plasmonic metal (Ag and Au) decorated silicon, designed for enhancing Raman signal. Following the discovery that only a partial amount of the electroactive material undergoes lithiation in the first cycle, we show that the plasmonic metal tips can enhance the connectivity of the Si particles. The micro-Raman mapping of electroactive silicon material reveals how the plasmonic metals influence the distribution of silicon active sites during battery cycling. The ratio of electroactive Si is found to increase from Si to Si/Au and Si/Ag electrodes, and the results are explained in terms of interconnectivity of the particles.

No abstract

Silicon is predicted to become a significant component of high energy density Li-ion anodes. Mn-based cathodes for Li-ion batteries have been widely investigated in past years and Mn dissolution into the electrolyte, migration, and deposition on the anode's solid electrolyte interphase present a major challenge. In this work, we intentionally synthesize manganese oxide with several nanoscale thicknesses on a Si nanomaterial and follow the electrochemical behavior of the core−shell nanoparticles as Li-ion anode. The structure of the nanocomposites is investigated using highresolution scanning electron microscopy, high-resolution transition electron microscopy, X-ray diffraction, and electron paramagnetic resonance. The synthesis yields uniform nanoshells of Mn 3 O 4 haussmanite phase. We demonstrate that the haussmanite phase is electrochemically active, and its presence improves the lithiation process during cycling. This study reveals that the formation of a thin shell of manganese oxide phase on Si anode can improve the lithiation kinetics of the Si nanomaterials, while a thicker shell slows down the kinetics. In summary, to a certain extent, the contamination of Si anode materials from Mn-based cathodic materials could have a positive impact on their electrochemical behavior.