Synthesis Of Molybdenum-based Nanomaterials And Their Electrochemical Performance For Lithium/Sodium Ion Batteries

Molybdenum-based sulfide and oxide materials have attracted much attention for lithium ions storage due to its relatively high energy density(800-1000 mA h/g).However,these Molybdenum-based materials suffer from low electronic conductivity and severe volume expansion during repeated Li+ inseretion/extraction.nanostructure fabrication is certified as a effective way to solve these problems.In the paper,we synthesized a series of Molybdenum-based nanostructures by a facile hydrothermal method such as Molybdenum disulfide nanotubes,Molybdenum disulfide nanoflowers and Molybdenum dioxide nanoparticles,and investigated their electrochemical capabilities for lithium/sodium ion batteries.1.MoS2@C nanotube is prepared through a facile hydrothermal method via the Kirkendall Effect with MoO3-EDA as a precursor,the MoS2 nanotube is composed of MoS2 nanosheets.When evaluated as an anode material for lithium ion batteries(LIB),the MoS2@C nanotube manifests an enhanced capacity of 1326.9 mA h g-1 at 0.1 C with high Coulombic efficiency of 92%and with capacity retention of 1058 mA h g-1 after 300 cycles at a rate of 0.5 C.A superior rate capacity of 850 mA h g-1 at 5 C is also obtained.The good lithium storage performance of MoS2@C nanotube suggests can be mainly attributed to its synchronically formed amorphous carbon and the stable hollow structure.The formed amorphous carbon can limit the amount of solid electrolyte interface(SEI)layer and improves the electronic conductivity of the composite,while the hollow structure can reduce the distance of Li+ diffusion and alleviate the volume expansion during repeated Li+ intercalation/deintercalation.2.Uniform MoS2 nanoflower is prepared through a hydrothermal method with the help of PVP following by high temperature calcinations.Each MoS2 nanoflower is accumulated from MoS2 nanosheets.The MoS2 nanoflower anode material suggests a high capacity of 1038 mAh/g under a current density of 100 mA/g.After cycling for 100 cycles,the capacity remains 890 mAh/g.A good rate capacity of 850 mA h/g at 5000 mA/g is also obtained.Above good electrochemical performance is a result of its specific nanoflowers structure,which can reduce the distance of Li+diffusion and accelerate Li+ transmission,furthermore,it can somewhat alleviate the volume expansion during electrochemical reactions.3.Uniform MoO2 nanoparticles were synthesized and evaluated as anode material for high safety lithium ion batteries..By cutting off the potential window between 1.0 V-2.5 V,the as-prepared MoO2 anode shows intercalation-type lithium intercalation/deintercalation reaction with no conversion-type reaction happened,which will greatly improve its long-term cycle stability.And working at this voltage range will avoid the serious security problems owing to the growth of lithium dendrites and will prevent the formation of solid-electrolyte interface(SEI)layer.MoO2 nanoparticles show comparable high capacity of 226 mA h/g at 0.1 C and ultra-long cycle life with only 4%capacity decay over 7000 cycles at a high rate of 5 C.To further verify the feasibility of this anode material for practical application,we assembled a full cell composed of the as-prepared MoO2 anode and commercial LiCoO2 cathode.As expected,the full cell gives a relatively high energy density 179 Wh/Kg based on total mass of active materials of MoO2 anode and LiCoO2 cathode,and after 500 cycles,it shows 87% capacity retention.