Fabrication Of Plant Based Porous Carbon Composite And Study On Its Anode Performance In Lithium Ion Battery

Porous carbon materials are featured by high specific surface areas, stable physical and chemicalproperties and 3D interconnected porous structure. They can provide channels to efficiently transport protons, liquids and gases. These materials have become the most significant materials which can be utilized as electrodes of lithium-ion battery（LIB）, absorbent and catalyst. Research and development on porous carbon have become a hot topic.By pore diameter, porous carbon can be divided into three groups: macro-porous（>50nm）, meso-porous（2-50nm） and micro-porous（<2nm） carbon. Macro-porous structure provides channels for molecule exchange, meco-porous structure for ion exchange through capillary phenomenon, while micro-porous structure is where the reactions take place. Hierarchical porestructure can provide enough reaction sites under the prerequisite that the material exchanges are taking place. The structure character of porous carbon could meet the demand of effective colligability and designability as lithium ion battery. Currently, porous carbon is artificially synthesized through complicated processes. The pores in such artificially-made materials are scattered in a single and homogeneous pattern. In addition, they are made by aperiodic carbon with poor electrical conductivity. Natural materials are rich in resources, low in cost, renewable and in concord with the environment. It has many advantages to make hierarchical porous carbon materials with natural biological templates. The biological templates are both organic and inorganic. The organic natural polymers are the carbon source. The pore structure could be created through the removal of inorganic component. Furthermore, amorphous carbon can be catalyzed to graphite layers by the introduction of catalytic. It improves not only the electronic conductivity, but also other related properties because the formation of graphitic layer increases the exposure of surface area to the media. Based on these ideas, rice husk is chosen to be the precursor because of its ideal 3D network structure and high global production（0.135 billion tons per year）. Through carbonization, activation and catalyze, rice husk can be fabricated into porous carbon which content 3D interconnect hierarchical and in situ grapheme-like structure（GRHC） with specific surface area of ⁹00 m2g-1. In addition, GRHC-Fe₂O₃ can be fabricated by finding the intersection of anode material for LIBs and graphitizing catalyst for amorphous carbon. Furthermore, carbon-coated GRHC-Sn O₂@C composite can be designed and prepared by focus on the main fading mode of Sn O₂ anode material. To further test the designability of this unique matrix improve its conductivity and explore its dual functions as LIB anode material based on rice husk carbon,nanocomposite loaded on activated（magnetic） nanoparticle N-RHC-AN is fabricated. It presents excellent reversible capacity and cycling performance as LIB anode material. The thesis mainly focuses on the following aspects:1. Based on the observation of the original and carbonized structure of common plants, such as rice husk, water hyacinth, water bamboo leaf, and analysis and comparison of their specific surface areas, pore diameter distribution and pore structure, rice husk is chosen as the raw material for porous carbon because carbonized husk has higher specific surface area and ideal hierarchical pore structure. Besides, rice husk is produced in huge quantity and wildly spreads all over the world. The GRHC is prepared under an optimizedmethod: carbonization in 650℃, activation by potassium hydroxidein 800 ℃ and graphitization catalyzed by ferric nitrate in 800 ℃.2. The influences of different iron malysite concentration on the structure and cycling performance and different calcination temperature on the structure of nanocomposite during the one-port fabrication process of GRHC-Fe₂O₃ were studied. The result shows, GRHC-Fe₂O₃ nanocomposite with 10 wt% Fe₂O₃ content have the major priority on the purpose of obtain homogeneous graphene like network Fe₂O₃ nano-particle and considerable capacity, which performed 623 m Ah g-1 under 50 m A g-1 and 450 m Ah g-1 under 1000 m A g-1 after 100 cycles.3. Unique GRHC-Sn O₂@C composite consists of hierarchically porous structure, graphene-like network, well dispersed nano-particle and carbon coating were fabricated based on GRHC by means of precursor impregnation ultrasonic treatment hydro-thermal and calcination process. The GRHC-Sn O₂@C nanocomposite shows considerable capacity and retention even under severe condition. The capacity of 400 m Ah g-1 under 1 A g-1current density could be obtained after 100 cycles. The fabrication and excellent performance of GRHC-Sn O₂@C confirmed the advance and designability of GRHC matrix.4. For the purpose of checked the graphitization of additive carbon on RHC and consider both anode activity of LIB and the absorbent of heavy metal ion, N-RHC-AN nanocomposite combining N-doped graphene-like structure Fe3O4&Fe functional particle and hierarchical porous architecture was fabricated through PPy absorbent polymerization and following calcination process. When used as an anode material for lithium batteries, N-RHC-AN nanocomposite delivered a reversible capacity of⁵10 m Ah g-1 after 10 cycles thencontinue activationduring the following cycles and obtained reversible capacity of ⁶10 m Ah g-1 even after 100 cycles.Guided by hot topic, energy, this thesis discusses the fabrication of graphitized porous carbon which has high specific surface area, 3D interconnected hierarchical porous structure and in situ 3D graphene like network with good electric conductivity. Rice husk, which has ideal hierarchical pore structure and high production volume, has been chosen as the optimal raw material for porous carbon based on the idea of using hierarchical porous-structured plants as the template and the analysis of microstructures of various agricultural wastes such as rice husk, straw and water bamboo leaf. Ferric salt is important in the fabrication due to its electrode activity and its properties as catalyze and graphitizing material. Graphitized porous carbon can be further nano-composited, coated, nitrogen-doped or structurally or functionally designed to fit the detailed requirements when applied into LIB anode. N-doped porous carbon nanocomposite which served as great cycling performance anode material of LIB is successfully fabricated with excellent and stable properties. This thesis puts into practice the research idea of referring to the nature, and designing and changing the natural properties for specific practical use. It has achieved good results and thus provided new research directions for materials in energy industries.