Three-Dimensional Flower-like MoS2 Nanosheets Grown on Graphite as High-Performance Anode Materials for Fast-Charging Lithium-Ion Batteries.

The demand for fast-charging lithium-ion batteries (LIBs) with long cycle life is growing rapidly due to the increasing use of electric vehicles (EVs) and energy storage systems (ESSs). Meeting this demand requires the development of advanced anode materials with improved rate capabilities and cycling stability. Graphite is a widely used anode material for LIBs due to its stable cycling performance and high reversibility. However, the sluggish kinetics and lithium plating on the graphite anode during high-rate charging conditions hinder the development of fast-charging LIBs. In this work, we report on a facile hydrothermal method to achieve three-dimensional (3D) flower-like MoS2 nanosheets grown on the surface of graphite as anode materials with high capacity and high power for LIBs. The composite of artificial graphite decorated with varying amounts of MoS2 nanosheets, denoted as MoS2@AG composites, deliver excellent rate performance and cycling stability. The 20-MoS2@AG composite exhibits high reversible cycle stability (~463 mAh g-1 at 200 mA g-1 after 100 cycles), excellent rate capability, and a stable cycle life at the high current density of 1200 mA g-1 over 300 cycles. We demonstrate that the MoS2-nanosheets-decorated graphite composites synthesized via a simple method have significant potential for the development of fast-charging LIBs with improved rate capabilities and interfacial kinetics.

Preparation and phase transition of FeOOH nanorods: strain effects on catalytic water oxidation.

The evolution of the phase and morphology of FeOOH nanorods prepared by a hydrothermal method is studied via X-ray diffraction (XRD) and in situ transmission electron microscopy. The FeOOH nanorod with a tetragonal structure (ß-FeOOH) is gradually converted into a rhombohedral Fe2O3 nanorod by a simple thermal treatment. The existence of an intermediate FeOOH structure with high lattice strains during the phase transition is identified by Rietveld analysis using XRD. The electrochemical properties of the nanorods are investigated based on the crystal phases to elucidate their relative catalytic activities. The strained-FeOOH nanorods exhibited enhanced catalytic water oxidation activity and stability. Typically, the strained-FeOOH nanorods showed high electrochemical stability under neutral conditions, while tetragonal FeOOH nanorods under the same conditions showed rapid deactivation for water oxidation reaction.

Spontaneous phase transition of hexagonal wurtzite CoO: application to electrochemical and photoelectrochemical water splitting.

The addition of water initiates the phase transition of hexagonal CoO to Co(OH)2 nanocrystals. Inducing the phase transition of h-CoO on various substrates results in efficient chemical bonding between Co(OH)2 and the substrate. The efficient deposition of Co(OH)2 is widely applicable for electrochemical and photoelectrochemical water oxidation reactions.