Controlled Structure And Property Study Of Molybdenum And Tin Based Anode Materials Of Lithium Ion Batteries

With the rapid development of global industrialization, the energy shortage and thepollution of environment have been an important issue for the present human.Considerable recent attention has focused on environmentally friendly energyresources in an attempt to relieve the pressures of increasing oil demand, the depletionof non-renewable resources, and environmental pollution. However, these energyresources, such as wind energy, solar energy and tidal energy, are intermittent and,hence, are not convenient for direct use. Hence, large-scale energy storage stations arekey components for the conversion-storage-usage chains to implement their stable andefficient utilization.Among all of the available energy storage stations, lithium-ion batteries (LIBs)represent the state-of-art technology in rechargeable energy-storage devices and theycurrently occupy the promising position in the marketplace for powering anincreasingly diverse range of applications, from portable electronic devices to electricvehicles and hybrid electric vehicles. Such fast development of these applications hasled to increasing demands being placed on advanced active electrode materials owingto their crucial roles in the electrochemical performance of LIBs. With respect to theanodes of LIBs, increase of reversible storage capacity, improvement of rate capability,and achievements of stable cycling retention should be taken into account to obtainhigh performance LIBs. The lower specific energy and the charge/discharge rate ofthe present commercial graphite severely limit their use in many applications, such aselectric vehicles and smart grids where batteries are needed to store energy fromrenewable source of intermittent nature. In allusion to these problems, we havedesigned a variety of micro and nano structured materials with high specific capacity,and carried out characterization about structure, morphology and composition.Through the study of electrochemical performance of as-synthesized materials, wesystematically studied their lithium ion storage performance. The present work ismainly divided into the following four aspects:(1) Based on Ostwald ripening and oriented attachment growth mechanism, weprepared a well-designed two-dimensional nanosheet assembled SnO2hollowmicrospheres and interconnected core-shell structured MoO2hierarchicalmicrocapsule assembled by one-dimensional nanorod without any template and surfactant. These materials integrate three beneficial features: carbon-free, hollowcavity and porous shell. Due to their unique nanostructure, when evaluated forlithium-storage, they exhibit a high specific capacity at the higher rate conditions.(2) We report an interesting approach for efficient synthesis of interconnectingnanosheets assembled SnO2microtubes. On the basis of self-sacrificial templatetechnology, the SnO2microtubes were successfully synthesized via a surfactant-freeand one step hydrothermal route using natural biological substance as templatewithout anything post treatment (high temperature or strong acid and base). Theseas-synthesized SnO2microtubes integrate two beneficial features: hollow cavity andporous shell, which accommodated large volume variation and facilitated fast and fullelectrolyte access to SnO2nanosheets. When evaluated for lithium ion batteries, theyexhibit high reversible capacity and good cycle performance.(3) Much attention has recently been focused on the synthesis and application ofgraphene analogues of layered nanomaterials due to their better electrochemicalperformance than bulk counterparts. Here we synthesize graphene analogue ofthree-dimensional MoS2hierarchical nanoarchitectures via a facile hydrothermal route.The graphene-like MoS2nanosheets are uniformly dispersed in amorphous carbonmatrix produced in situ by the hydrothermal carbonization. The interlaminar distancebetween MoS2nanosheets is about1.38nm, which is far larger than that of bulk MoS2(0.62nm). Such a layered architecture is especially beneficial to the intercalation anddeintercalation of Li+. When tested as a Li-storage anode material, the graphene-likeMoS2hierarchical nanoarchitectures exhibit high specific capacity, superior ratecapability, and enhanced cycling performance. This materials shows a high reversiblecapacity of973.8mAh g-1at the current density of1000mA g-1after100cycles.(4) Based on an in situ growth constructing strategy, hierarchical SnO2nanosheetarchitectures have been fabricated on a three-dimensional macroporous substrate. Theas-prepared hierarchical SnO2nanoarchitectures on the nickel foam can be directlyused as an integrated anode for lithium ion batteries without the addition of otherancillary materials such as carbon black or binder. In view of their apparentadvantages, such as high electroactive surface area, ultrathin sheet feature, robustmechanical strength, shorter ion and electron transport path and the specificmacroporous structure. The hierarchical SnO2nanosheets exhibit excellent lithiumstorge performance. Our present growth approach offers a new technique for thedesign and synthesis of transition metal oxide hierarchical nanoarrays that are promising for the electrochemical energy storage electrode without carbon black andbinder.