Synthesis Of Iron Based Carbon Nanocomposites As Lithium Storage Materials

Lithium-ion battery is one of the important components as energy storage and conversion devices for new energy development and sustainable utilization,which has been greatly promoted the transformation of life style and social development.However,with the rapid development of economy and society,higher requirements are necessary for the current lithium-ion battery,such as energy density,cycle performance,rate performance and safety and so on.Therefore,it is essential to develop new electrode materials for lithium-ion battery with high power and energy density.Transition metal compounds have superior potential for lithium-ion storage for practical application.Among the compounds of transition metal elements,iron based composites have been widely studied.However,iron-based electrode materials have not been large-scale practically applied due to its own poor conductivity and crack from volume expansion during cycling process.So nanoengineering of the current iron-based compounds or adding some strong conductive materials to improve the conductivity of iron-based composites and buffer the volume expansion of materials for enhanced electrochemical performance.Herein,two iron-based carbon nanocomposites were designed and synthesized.We have carefully investigated the reaction mechanism,morphology and microstructure of iron-based carbon nanocomposites.We also investigated the electrochemical performance by galvanostatic charge/discharge and cyclic voltammetry test.Finally,we fabricated new electrode materials with high specific capacity,superior cycle and rate performance by optimizing the experimental procedures.Detailed contents are as follows:1.In this work,we have demonstrated a two-step procedure for the facile synthesis of mesoporous hybrids comprised of 75%Fe₃O₄a nanorods and 25%reduced graphene oxide.The structural features of this composite are characterized by the covalent bonding between the rGO sheets and metal oxide,wrapping metal oxide nanorods by rGO sheets and hierarchical self-assembly into robust mesoporous ensembles.The material has been systematically tested as an lithium-ion battery anode component.A high reversible capacity of 1053mAhg^-1 subjected to 250 charge-discharge cycles at 500mAg^-1 was achieved,accompanied by an excellent rate capability with the deliverable energy of 788-541 mAhg^-1 upon the application of high current densities of 1000-5000mAg^-1.2.In this work,we have successfully synthesized the core-shell nanostructured C@Fe₇S₈ nanorods using a facile one-pot process by exploiting solid-state chemical sulfurizing of an iron-based MOF precursor.The resulting core-shell nanorod is composed of approximately 13%carbon and 87%Fe₇S₈ with a hierarchically porous structure.When assembled redox conversion-type lithium-ion battery,this composite material has demonstrated high lithium-ion storage capacity of 1148 mAhg^-1 under the current rate of 500mAg^-1 for 170 cycles and an impressive retention capacity of 657 mAhg^-1 with a current density of 2000 mAg^-1.