Synthesis And Application Of Nanomaterials As Electrodes For Lithium Ion Batteries

Lithium ion batteries have attracted intensive attention for their merits includingclean, high efficiency and energy density, with the increasing urgency of the globalenvironmental and energy crisis. The research and development of electrode materialswith high energy density, high power capability, good safety, long durability and lowcost are the key challenges towards the development and application of lithium ionbatteries. Several electrode nanomaterials including Li4Ti5O12, Fe2O3, Sn-based alloys,LiMO2and LiMn2O4have been regarded as candidates for the electrode materials ofnext-generation lithium ion batteries, for their advantages of high rate, high safety andlow cost. In this dissertation, several synthetic methods have been established forabove-mentioned nanomaterials to improve the comprehensive performances.A low-temperature solid state method has been developed forLi4Ti5O12nanocrystals. A metastable nanocrystals cubic Li₂TiO₃has been chosen as theprecursor. By investigating the Li+-H+exchange reaction, stability to heat as well asconversion temperature of cubic Li₂TiO₃, Li4Ti5O12nanocrystals has been prepared bysolid state reaction under relative low temperature. Li4Ti5O12nanocrystal has showninspiring high rate capability with162mAh/g under5C, due to its large surface areaandsmall size.A solvothermal method for Fe2O3nanodiscs has been investigated. By tuningsynthetic conditions, the growth direction of Fe2O3has been confined in a-b plane andeventually grown to nanodiscs, following Ostwald ripening mechanism. NanosizedFe2O3nanodiscs exhibit high electrochemical reactivity as well as outstandingcyclingand rate capabilities, delivering540mAh/g after150cycles under600mA/g and280mAh/g under2400mA/g.A hydrothermal method has been proposed for SnS nanobelts. SnS nanobelts haveformed via growing along [020] direction under well controlled condition, observingOstwald ripening mechanism. SnS nanobelts have shown sound flexibility andelectrochemical properties, and the one-dimensional structure has been well preservedafter cycles of volumetric expansion due to Li+insertion due to the flexibility ofnanobels for strains.Approach for surface-Li₂TiO₃-rich LiMO2nanobelts has been established. A series of mixed metal oxalate nanobelts has been prepared as precursor, and coating methodhas been designed based on the thermal decomposition property of the precursor; viasolid state reaction surface treated LiMO2nanobelts have been obtained.Surface-Li₂TiO₃-rich LiMO2nanobelts have exhibited excellent rate and cyclingcapabilities, because the coating materials Li₂TiO₃is stable with electrolyte and has athree-dimensional Li+diffusion path which help to reduce the surface charge transferand reduce the surface side reaction.Approach for constructing LiMn2O4nanorods combined with coating and dopingtreatment has been proposed. Li₂SiO₃coated nanorods and Li-Ti-Mn-O coated nanorodswith Ti4+doping have been prepared applying MnOOH as the precursor. The coatingmethod is also based on the thermal decomposition reaction of MnOOH. ModifiedLiMn2O4nanorods have inspiring electrochemical performance, due to the reducedsurface charge-transfer resistance by Li₂SiO₃and Li-Ti-Mn-O, and increased structuralstability by Ti4+doping.