Research Of Carbon-based Anode Materials For Sodium Ion Batteries

Because of the abundant raw material resources, low cost and high specific capacity,sodium ion battery is considered as the most suitable secondary battery for large scale energy storage system. Compared with the cathode materials, the study on the anode materials has lagged behind. Development of the anode materials with high capacity, long life and excellent rate properties is the key to advocating practical application for sodium ion batteries. In this paper, in terms of controlling layer distance, heteroatom doping,establishing nano porous structure and combing with metal oxide composite, around the carbon anode materials for sodium ion battery, 5 kinds of carbon-based materials were prepared, including nitrogen-doping carbon/graphene composites, nitrogen-doped porous carbon materials, floral variant of mesoporous carbon, biomass-derived nitrogen-doped mesoporous carbon materials and Fe3O4 quantum dots/graphene composites. The electrochemical sodium storage performance of the carbon-based materials was studied,and the effect of the composition and the structure of the carbon anode materials on the electrochemical performance was investigated.(1) Nitrogen-doped carbon/graphene (NCG) hybrid materials with sandwich structure were prepared from aniline solution with graphene oxide by in-situ polymerization and the followed pyrolysis. The NCG has a large interlayer distance (0.360 nm) and a high nitrogen content of 7.54 at%, resulting in a high reversible sodium storage capacity of 336 mAh g-1 at 30 mh g-1. The graphene with high electronic conductivity closely coating on nitrogen-doped carbon nanosheets in the sandwich-like structure of NCG guarantees fast electron transport, endowing the NCG with excellent rate capability (94 mAh g-1 at 50 mA g-1). The NCG also exhibits good cycle stability with a capacity retention of 89 % after 200 cycles at 50 mA g-1.(2) Nitrogen-doped carbon with interconnected mesoporous structure was simply prepared via a nano-CaCO3 template method. The preparation process includes in situ polymerization of aniline in a nano-CaCO3 aqueous solution, carbonization of the composites and removal of the template with diluted hydrochloric acid. Nitrogen sorption test shows the prepared carbon has porous structure, and the X-ray photoelectron spectroscopy analysis indicates that the carbon has a high nitrogen content of 7.78 at. %.The nitrogen-rich mesoporous carbon derived from polyaniline shows a high reversible capacity of 338 mAh g-1 at a current density of 30 mA g-1, and outstanding cycling durability (110.7 mAh g-1 at a current density of 500 mAh g-1 after 800 cycles).(3) The floral variant of carbon with high specific surface area and developed mesoporous structure was simply prepared by direct pyrolysis of zinc citrateunder inert atmosphere. The nano ZnO produced from zinc citrate during the pysolysis can act as mesopore template, and the obtained carbon shows a BET surface area of 1382 m2 g-1 and a pore volume of 2.02 m3 g-1. The unique floral microstructure, developed mesopores and large layer distance (0.42 nm) endow the carbon with ultrahigh reversible capacity and superior rate performance. The floral variant of mesoporous carbon exhibits a reversible sodium storage capacity as high as 438.5 mAh g-1 at a current density of 30 mA g-1 and retains a value of 68.7 mAh g-1 at an enhanced current density of 10 A g-1.(4) Carbon materials with high nitrogen content and developed mesopores were simply prepared from shrimp skin by direct pyrolysis under inert atmosphere. The shrimp skin is a natural organic/inorganic nano composite material composed of collagen and inorganic minerals. The collagen transfers into nitrogen-rich carbons in the pyrolysis process and the evenly dispersed inorganic minerals act hard templates to produce abundant mesopores. As the pyrolysis temperature increases, the specific surface area and pore volume rises and the nitrogen content decreases. The sample obtained at 700 ? has both a large specific surface area of 531 m2 g-1 and a high nitrogen content of 7.25 at%, promising outstanding performances for electrochemical sodium storage. The reversible sodium storage capacity reaches as high as 434.6 mAh g-1 at 30 mA g-1 with excellent cycle durability and rate capability. These results indicate the creative utilization of natural nanocomposites is a facial, low cost and sustainable strategy for the synthesis of high performance anode materials for sodium ion batteries.(5) 3D-0D graphene-Fe3O4 quantum dot hybrids were fabricated by a facile one-pot hydrothermal approach. In this composite, Fe3O4 quantum dots with an average size of 4.9 nm are anchored on the 3D structured graphene nanosheets homo geneously. The 0D Fe3O4 quantum dots have high electrochemical activity and relatively small volume change during the charging-discharging process; the 3D graphene can inhibite Fe3O4 particles aggregation and accommodating their volume change during the charging-discharging process, as well as enabling fast diffusion of electrons and rapid transfer of electrolyte ions. Consequently,the 3D-0D graphene-Fe3O4 quantum dot hybrids exhibit ultrahigh sodium storage capacity(525 mAh g-1at 30mA g-1), outstanding cycling stability (312 mAh g-1 after 200 cycles at 50mA g-1) and superior rate performance (56 mAh g-1 at 10 A g-1).