Study On Synthesis And Electronic Properties Of Binary Oxide Micro And Nano Materials

Amongst all of the commercially available energy-storage devices, lithium-ionbatteries(LIBs) represent the state-of-the-art technology and have occupied the prime positionin the marketplace for powering an increasingly diverse range of applications, from portableelectronic devices (such as laptops, personal digital assistants, and cellular phones) to electricvehicles (EVs) and hybrid EVs (HEVs). However, the fast development of these fields putsforward higher requirements for advanced LIBs in terms of higher energy/power densities andlonger cycle life. Currently, the available anode materials are commonly limited tocarbonaceous materials in the commercial lithium-ion-batteries (LIBs). However the lowertheoretical capacity of graphite is limited to372mAh g-1, which is low relative to therequirement of high-energy application fields. The development of superior electrode materialscould be one of the most-effective ways to improve the performance. Because transition metaloxides have a high theoretical capacity as the electrode materials of LIBs, a worldwideresearch effort has been focused on improving their energy density, cycle performance andCoulombic efficiency. However, the practical use of bulk oxide materials is significantlyimpeded by the poor capacity retention over extended charge/discharge cycling. This problemmainly originates from the large volume change of electrode materials accompanying lithiuminsertion/extraction, which creates large internal stress, leading to the pulverization of theelectrode material. In the recent years, micro and nano structured materials have receivedmuch attention as an outstanding anode materials in LIBs in the field of new energy.In view of above mentioned problems, we have designed a variety of micro and nano-structured stannum and manganese based oxide anode by using a low temperature chemicalmethod. This paper is mainly divided into the following three aspects:(1) Synthesis of two-dimensional nanosheet tin dioxide: we synthesis two-dimensionalsheet-structured stannous oxide precursor materials under the condition of a lower temperatureby using the tri-sodium citrate and cetyltrimethyl ammonium bromide as surfactant. Themorphology of product has no change after heat post-treatment, which is easy to control andsynthetic conditions is easy. When evaluated for lithium-storage properties, they exhibit a highspecific capacity of580mAh g-1at a rate of0.5C after50cycles. (2) Synthesis of hexagonal structured manganese oxide materials: manganese oxalatedihydrate precursors have been synthesized through hydrolysis reaction in the mixed ofsolvent system including polyethylene glycol and ethanol, and MnCl2·4H2O as source ofmanganese. The porous structured Mn2O3and MnO material could be obtained by heattreating these precursors in ambient air and nitrogen, respectively. Above mentionedmicro-nano structures show a high specific capacity when as an anode materials in LIBs.(3) Synthesis of carbon fiber/manganese oxide composite: the manganese oxidenanosheets grow on the surface of fiber cloth by using an in situ growth method. After heattreatment under N2atmosphere, we can obtain the manganese oxide coated carbon fiberscomposite material. Because the manganese oxides grow on the surface of carbon cloth by anin situ construction strategy, the interface of two phase has a high contact area. The flexibleconductive substrate effectively solves the problem of a low electrical conductivity ofelectrode materials after carbonization. At the same time, the as-prepared composite can bedirectly used as an integrated anode for LIBs without the addition of other ancillary materialssuch as carbon black or binder. Such materials exhibit a good charge and dischargeperformance test for lithium ion batteries anode material.