Graphene/Acid Coassisted Synthesis of Ultrathin MoS₂ Nanosheets with Outstanding Rate Capability for a Lithium Battery Anode

Morphology-controlled MoS₂ nanosheets were successfully synthesized with the aid of graphene/acid coexistence by a one-pot hydrothermal method. The ultrathin MoS₂ nanosheets were self-assembled into a cockscomb-like structure with an exposed (100) facet on graphene sheets, which is in strong contrast to large aggregate MoS₂ plates grown freely on graphene sheets without acetic acid. The ultrathin MoS₂ nanosheets displayed excellent rate performance for Li storage (709 mAh·g^–1 capacity at 8320 mA·g^–1 discharging rate) and superior charge/discharge cyclability

Si/Ge Double-Layered Nanotube Array as a Lithium Ion Battery Anode

Problems related to tremendous volume changes associated with cycling and the low electron conductivity and ion diffusivity of Si represent major obstacles to its use in high-capacity anodes for lithium ion batteries. We have developed a group IVA based nanotube heterostructure array, consisting of a high-capacity Si inner layer and a highly conductive Ge outer layer, to yield both favorable mechanics and kinetics in battery applications. This type of Si/Ge double-layered nanotube array electrode exhibits improved electrochemical performances over the analogous homogeneous Si system, including stable capacity retention (85% after 50 cycles) and doubled capacity at a 3<i>C</i> rate. These results stem from reduced maximum hoop strain in the nanotubes, supported by theoretical mechanics modeling, and lowered activation energy barrier for Li diffusion. This electrode technology creates opportunities in the development of group IVA nanotube heterostructures for next generation lithium ion batteries