Preparation And Electrochemical Property Of Hierarchical Porous Carbon/Metal Oxide Composites

Transition metal oxides are potential and promising electrode materials of Li ion battery and supercapacitor,due to their higher theoretical capacity and charge-discharge capacity of the first cycle,high voltage and coulomb efficiency,excellent structure stability.However,the rate performace and cycle stability of these materials get worse for their lower conductivity of electrons and ions and nanoparticles aggregation.Hierarchical porous carbon materials manifest good ions diffusivity because of their conductivity and unique pore distributions.The micropores can strorage adundant ions for Li ion battery and supercapacitor.And themesopores or macropores can provide fast and efficient transport channels for ions charge and discharge.In this dissertation,combining the advantages of carbon and metal oxide,carbon/transition metal oxide composites with hierarchical porous and improved electrochemical properties were prepared the morphologies and structures of the composite materials were characterized by a variety of analysis methods.The influences of the the content of transition metal oxide and calcination temperature were studied in detail.The research contents are as follows:1.Hierarchical porous carbon-TiO₂（HPCT）composites have been successfully synthesized via evaporation-induced self-assembly（EISA）,using low molecular weight phenolic resin as carbon source,butyl-titanate as titanium source,and three block copolymer F127 as a template.The results showed thatboth micropores and mesopores with higher contents exsited in the HPCT composites and TiO₂ mainly dispersed in the walls of the porous carbon skeleton.The content of TiO₂ and calcinations temperature played significant roles on the structures and electrochemical properties.TheHPCT optimal TiO₂ content and calcination temperature of the HPCT composites were 28 wt.%and 600℃,respectively.Under these conditions,the as prepared TiO₂ was anatase phase with low crystallination degree.The composite showed larger specific surface area,the average pore size,pore volumeand,and proper ratio of miropores and mesopores..As the anode material of lithium ion battery,the discharge specific capacity of the composites reached 502.5mAh g^-1 for the firstcycle,and the specific capacity kept 376.9 mAh g^-1 after 50 cycles,which higher than the theoretical capacity of graphite.As the electrode materials of supercapacitor,the discharge specific capacity reached 90.4 F g^-1 at the current density of 0.1 A g^-1;and the capacitance retention was about 90%at the current density of 1 A g^-1.After treated by HF solution,the discharge specific capacity of HPCT-600-5HF reached 138.9 F g^-1 at the current density of 0.1 A g^-1.2.Using low molecular weight phenolic resin as carbon source,three block copolymer F127 as the template,porous carbon materials with hierarchical porous structure were prepared via EISA.Hierarchical porous carbon/CoO（HPCC）composites have been successfully synthesized by impregnation/adsorption method.The main conclusions were as follow.The optimal CoO content and calcination temperature of the HPCC composites were 1.2 wt.%and 400℃,respectively.The HPCC had the best electrochemical performance under this condition.As the anode material of lithium ion battery,HPCC-400-6 showed the highest discharge specific capacity,and after 50 cycles the specific capacity was 376.9 mAh g^-1 at 0.1 C.The electrochemical properties were decreased obviously for the composites with excessive amounts of CoO or calcinations at too high temperature.