Prepartion Of Hierarchical Porous Carbon Composite Materials Derived From Lead Citrate For Enhanced Supercapacitance Performance

Environment and energy are two most critical issues in our country that requires prioritizing our efforts and resources to address in the long-term. To address these challenges, wide application of renewable green energy with high performance and storage efficiency was believed the key to resolve serious environmental problems such as haze from the source.Supercapacitors, a new type of energy storage device, with a high energy density, high power density and other characteristics, desmonstrate wide applications. The electrochemical performance of the electrode material is the key to producing high energy density supercapacitors. To obtain the new supercapacitor electrode material, in this work, lead citrate synthesized from recycling of spent lead-acid battery via hydrometallurgical method was used as the carbon precursor, which was used to produce Hierarchical Porous Carbon(HPC) by the method of calcination and activation. The work focused on the characterization of HPC material and the evaluation of electrochemical performance. The content of this thesis contains the following three parts.1. Lead citrate synthesized from spent lead acid battery paste through acetic acid- sodium citrate leaching system was used as the carbon precursor. Lower temperature calcination in a nitrogen atmosphere was chosen to prepare a three-dimensional porous carbon material. Characterization and the electrochemical evaluation indicated that the specific surface area of the carbon material was increased with increasing calcined temperature, with fragmented columnar structure at very high tempertature. The capacitance performance of carbon materials synthesized from the lower temperature was poor at lower temparature and improved significantly when calcined temperature raised to 600 ?.2. To further enhance HPC electrochemical performance, physical activation and chemical activation method were used to modify the structure of the carbon material. Carbon material activated by KOH showed increased surface area to 866.59 m2/g, and mass specific capacitance 82.8F/g at current density of 1A/g. The lead cirate containning nanofiber synthesized by electrospinning was directly calcined in a nitrogen atmosphere to obtain carbon nanofibers, which showed a mass specific capacitance of 42.2 F/g. Nitrogen doping was also used to modify HPC. In this work a nitrogen containing phenolic resin and lead citratewere uniformly mixed at a mass ratio of 1:1. Electrochemical tests show that porous material synthesized from the lead citrate mixed with phenolic resin contained nitrogen functional groups and showed pseudocapacitance effect which lead to huge improvement of electrochemical performance. Benefit from the pseudocapacitance effect, porous carbon material presented a mass specific capacitance of 203.8 F/g at 100 mA/g current density.3. To enhancement the electrochemical performance further, manganese oxide was utilized to modify the HPC to obtain carbon/manganese composite(CM) electrode material for supercapacitors. In the experiment, two methods were utilized to prepare manganese oxide on HPC, hydrothermal and constant potential electroplating specifically. Characterization analysis and electrochemical characterization showed that manganese oxide were successfully loaded on HPC surface. The electrochemical performance of CM synthesized at room temperature and 120 °C showed a mass specific capacitance of 231.8 F/g at 10 mV/s scan rate, and the internal resistance is only 0.8 ?, superior to CM synthesized at higher temperature during hydrothermal systhesis. While CM prepared by electrochemical plating exhibited poor stability during charge and discharge at a higher current density.In this paper, the synthesis and modification of HPC were explored by calcinating lead citrate synthesized from spent lead acid battery paste through acetic acid- sodium citrate leaching system, followed by activating and modifying with manganese dioxide, and the electrochemical performance of prepared electrode materials was investigated for supercapacitors. This work provide a new route to solve the environmental issue at the origin of pollution from the renewal energy and energy storage aspect.