Synthesis And Electrochemical Performance Of LiFePO₄/C Composite With Biological Carbon Source

Lithium ion batteries provide a high energy density,higher voltage as well as a long shelf life compared to traditionally used lead acid,NiMH and NiCd batteries.Thus,they are a very promising energy storage system for our daily life.As one of the most important components in a battery,cathode materials have been investigated intensively in recent years as they play a key role in determining the cell voltage and discharge capacity in a battery.Lithium iron phosphate?LiFePO₄?with features of excellent thermal stability,non-toxicity,low cost and abundance in nature is one of the most promising cathode materials to be used in lithium ion batteries.LiFePO₄/C composite was synthesized via self-assembly evaporation method with three kinds of morphologies and structure biological carbon sources.In order to investigate the morphology and structure,the composites were tested by X-ray diffraction?XRD?,scanning electron microscope?SEM?.The coin-type cells were assembled with the composite as cathode material,and the cells were tested with galvanostatic charge-discharge,cyclic voltammograms?CV?and electrochemical impendence spectroscopy?EIS?to verify the influence of the structure on the electrochemical performance.During the synthesis of LiFePO₄/C composite with the carbon source of granular biomass,higher discharge capacity will be got by selfassembly evaporation than that by impregnation method.LiFePO₄/C composite exhibits excellent structure and electrochemical performance synthesized with the carbon source of green algae.Compared with other fibrous biomass,LiFePO₄/C composite with 5 wt% cotton fibers will have a more appropriate structure for the intercalation and deintercalation process of Li+ and higher discharge capacity.A porous LiFePO₄/C composite has been achieved with the carbon source of bamboo film and delivered 153.7 mA h/g at the rate of 0.1C.