Preparation And Electrochemical Characterization Of Manganese-based/Carbon Nanocomposites

With the increasing demand for high performance and long cycle life of lithium-ion batteries,extensive efforts have been devoted to exploring new types of lithium-ion battery electrode materials.Among them,manganese-based materials have attracted increasing attention for its high theoretical specific capacity,appropriate conversion potential,earth-abundant,low-cost and safety.However,manganese-based materials still face great challenges in practical applications.And the challenges are poor intrinsic conductivity and large volume expansion.Currently,the main research focuses on the design of nano-structure and carbon coated electrodes.In this paper,we have prepared MnO2 nanowires and hollow MnO2 nanorods.To address the problems of manganese-based material,manganese-based/carbon composites have been widely developed.The main work of this paper are as follows:(1)The Mn02 nano wires were prepared by hydrothermal method,and the influence of hydrothermal temperature on the morphology of Mn02 nanowires was preliminarily investigated.Subsequently,the C/MnO nanofiber composites were prepared by electrospinning technique.The effect of MnO2 nanowires on structure and electrochemical performance of C/MnO composites is investigated.As a result,the composite shows excellent performance with the reversible capacity of 556 mA h g-1 at 100 mA g-1.(2)To increase the MnO mass loading,we prepared C/MnO nanorods composite through electrosping technique.The C/MnO nanorods composite shows excellent performance with the reversible capacity of 804 mA h g-1 at 100 mA g-1 after 100 cycles.When the current density is increased to 2000 mA g-1,the reversible capacity can still maintain 268 mAh g-1.(3)The MnO2@C@MnO nanorods composite was prepared by a simple and controllable approach involving subsequent hydrothermal reaction,poly dopamine-derived carbon coating and chemical deposition processes.The effect of coating time(carbon layer thickness)on the properties of the material was studied in detail.The triple-co-axial MnO2@C@MnO nanocomposite shows excellent lithium storage capabilities with the high reversible specific capacity of 919 mA h g-1 at 200 mA g-1 after 100 cycles,good rate performance(388 mA h g-1 at 2 A g-1)and an outstanding specific capacity(1243 mA h g-1)at the rate of 1 A g-1 after long-term cycles(900 cycles).