Synthesis Of Biological Materials Derived Carbon And The Application In Carbon/Sulfur And Carbon/Oxides Electrodes

Lithium-ion batteries (LIBs) are widely used in the portable electronic devices. However, the application of LIBs in power sources is still hampered by the low specific capacity, poor cycle performance and rate capability. Sulfur and oxides have attached much attention for their high specific capacity. However, the poor conductivity of sulfur and oxides is a great obstacle to the commercial application. Carbon materials are usually selected to improve the electrochemical performance of electrode materials but limited by complicated synthesis process. In this paper, biological materials are used as green templates and renewable carbon sources to construct carbon/sulfur, carbon/oxide composite electrode materials. The prepared materials show excellent electrochemical performance. The main results are as below:1) A simple method is developed to fabricate the Kapok fiber derivedcarbon nanotiles (KFCNTs) with Kapok fibers (KFs) as templates andcarbon sources. The as-prepared KFCNTs reveal an amorphous naturefor the carbon. Meanwhile, KFCNTs exhibit scale-like structure with high specific surface area.2) KFCNTs are used to construct sulfur composites. Compared with normal carbon/sulfur materials, KFCNTs/S exhibit high volumetric capacity because KFCNTs contain more sulfur. After90cycles, the KFCNTs/S (93.2wt%) cathodes show capacity retention of95.4%, displaying great cycle performance. The enhanced cyclability can be attributed to the follow three factors:(1) KFCNTs improve the conductivity of composite;(2) KFCNTs can accommodate some volume expansion of sulfur;(3) The outward migration of dissolved polysulfides may be retarded by the KFCNTs.3) An approach combined immersion and coating is used to synthesize Iron oxides/Carbon (IOC) with Eiehhornia erassipes as templates and carbon sources. Microstructure analyses of IOC show that iron oxides particles are tightly embedded into the carbon matrix derived from Eiehhornia erassipes with a carbon coating. The existence of carbon not only improve the conductivity of iron oxides but also restrain the volume expansion effectively. As the anode materials in LIBs, IOC materials deliver472.2mA h g-1after50cycle at0.1A g-1. When the current density rises to1A g-1, the discharge capacity still retains at286.7mA h g-1, illustrating favorable electrochemical performance.