Preparation And Electrochemical Properties Of Carbon/Polyaniline(Molybdenum Carbide) Composites

Li-ion batteries and supercapacitors,as a new generation of energy storage and conversion devices,had become research hotspot in electrochemical energy storage applications due to their fast charge/discharge rate and long cycling stability,and so on.The electrode materials are usually the vital composition of Li-ion batteries and supercapacitors,which plays a key role in the electrochemical performance.Graphene based composite materials,as one of the most widely used electrode materials,have excellent electrical,thermal and mechanical properties.However,graphene interface bonding with other materials is not very strong and is easy to fall off in the process of charge/discharge,which limits its further application.In this thesis,C/PANI and C/Mo2C composites with layered structure and high electrical performance were prepared through different synthetic methods.The layered structure can well solve the problem of poor combination between two interfaces.Their structures were characterized by SEM,TEM,XRD,FTIR and other techniques.Then,they were used as electrode materials for supercapacitors and Li-ion batteries,respectively,and their electrochemical performances were aslo investigated in details.Our main work is as follows:First of all,we use graphene oxide as a carrier of nano-sized polyaniline deposition and then graphene oxide/PANI composite with layer-by-layer structure was synthesized through vacuum self-assembly and situ polymerization.Graphene oxide can also provide the favorable conditions for polyaniline deposition,due to its high surface area and vast containing-oxide functional group.The special layer-by-layer structure can not only provide more ion transport channel,but also inhibit volume expansion of active materials in the process of charge/discharge.In addition,we investigated different content of PANI and different concentration of aniline on the effects of microstructure and electrochemical property.The specific capacitance of GP-50 composite can reach 780 F·g-1 at current density of 0.5 A·g-1 and keep 500 F·g-1 at current density of 50 A·g-1 in 1 mol·L-1 H2SO4 electrolyte,showing high specific capacity and excellent rate capability.Secondly,a facile method in combination of vacuum drying technique and high-temperature process has been reported for the synthesis of N-doped Mo2C/C nanocomposite by using ammonium molybdate and graphene oxide as the sources of molybdenum and carbon,respectively.The layer-by-layer structure can effectively shorten the lithium ions and electrons transfer path,and play a very good inhibitory effect for the volume expansion in the process of lithium ion circularly embedded in/out active material.When applied as anode materials for LIBs,N-doped Mo2C/C nanocomposite can deliver a very high quality capacity and volumetric capacity,which remain as large as?713 mAh·g-1 and 756 mAh·cm-3 at current density of 0.5 A·g-1 and 0.42 mA·cm-2 after continuously cycling for 300 times,respectively,and far more larger than other materials.