Layer-by-layer Assembled MoO₂Nanocomposites And Their Lithium Storage Properties

MoO₂with a monoclinic structure is a very attractive candidate as a substitute of theconventional graphite anode in lithium ion batteries because if its low electrical resistivity,high chemical stability and high theoretical capacity. Nowadays, the main efforts onresearch MoO₂focus on how to improve its practical capacity, optimize its cyclingperformance as well as rate capacity. By reducing its particle size to nanoscale, thelithium-storage mechanism could be changed from the traditional insertion type toconversion type with a theoretical capacity increased from²09mAh g to838mAh g.MoO₂/CNTs nanocomposites have been synthesized successfully for the first time througha simple LBL assembly route followed by a heat treatment in reducing atmosphere, wherebythe pretreated CNTs serve as both substrate and template. The conditions for the synthesisof these nanocomposites were systematically explored. Possible reasons for improvedlithium storage performance were discussed.The unique structure of MoO₂nanoparticles grown on the CNTs is of high stabilitywhich render them a promising candidate for anode materials. The porous3Dinterconnected nanostructure of MoO₂/CNTs ensures not only effective electronconductivity in the CNTs but also good contact between active MoO₂/CNTs nanostructuresand liquid electrolyte. The electrochemical tests show that the as-formed hybrids exhibithigh capacity and excellent cycling performance as an anode for lithium ion batteries. Thespecific discharge capacity is as high as977.9mAh g at a current density of100mA g in the first cycle. Even at the current density of400mA g the specific capacity remains399.6mAh g after100cycles.Besides, thin films of MoO₂nanoparticles and graphene sheets are also created LBLassembly as binder-free anodes for lithium-ion batteries. Both anionic polyoxometalate clusters and graphene oxide nanosheets with oxygen functional groups on both basalplanes and edges are assembled into LBL films with the aid of a cationic polyelectrolyte.After a subsequent thermal treatment in a Ar/H2atmosphere, the hybrid MoO₂/graphenefilms with three-dimensionally interconnected nanopores are formed, which compriseultrafine MoO₂nanoparticles homogeneously embedded in the porous network ofgraphene nanosheets. When used as an anode for lithium-ion batteries, the MoO₂/graphenethin-film electrode shows superior electrochemical performances with high specificcapacity and excellent cyclability. A high specific capacity of675.9mAh g after100discharge/charge cycles is achieved, indicating a promising anode candidate forlithium-storage applications.