Synthesis And Performance Studies Of Nanosized Ferrous Material(LiFe_xO_y)

LiCoO2has been the most widely used cathode material in commercial Li-ionbatteries. Nevertheless, cobalt has economic and environmental problems that leave thedoor open to exploit alternative cathode materials, among which, LiFeO2with similarrock-salt structure to LiCoO2, has been paid more attention due to its highcapacity(282mAh g-1), most abundance, better safety, environmentally benignity, thermalsafety and non-toxicity of Fe. The research contents of this paper are as follows：1）In this work, nanosized α-LiFeO2were synthesized by a simple low-temperaturesolid state method. X-ray diffraction pattern, scanning electronic microscopy andtransmission electron microscope demonstrate that the products were pure nanoparticles.Electrochemical measurements showed that the initial discharge capacity was277.9,188.4, and158.2mAh g-1at0.1,1, and2C, respectively. Meanwhile, the α-LiFeO2nanoparticles exhibited improved cycle stability (123mAh g-1at2C after60cycles,which is the highest among the previous reported values). The high capacity, improvedrate performance and cycle stability can be attributed to the smaller particle sizes, whichcan facilitate the contact between active materials and the electrolyte, enhance lithiumand electron transport during cycling.2） LiFe5O8nanomaterials are successfully synthesized through an oxalicacid-assisted solid-state method. TEM demonstrate that the average particle size is about10nm with a fairly narrow size distribution. Electrochemical performance testing usingLiFe5O8electrodes exhibits super rate performance and excellent cycle life. Especially,the discharge capacity is as high as130mAh g-1after100cycles at the current densitiesof2C, which is the highest among the previous reported values.3）The synthesis of electrochemically active α-LiFeO2nanoparticles in absoluteethanol at ambient temperature was developed using LiOH·H2O and Fe(NO3)3·9H2O asstarting materials and characterized by X-ray diffraction, Scanning ElectronicMicroscopy, Transmission Electron Microscope. The electrochemical performance of theα-LiFeO2nanoparticles as cathode materials for lithium secondary battery showed thatthe initial dischargecapacity of α-LiFeO2(theoretical capacity of282mA10h g-1)nanoparticles was290.6,194, and183.8mAh g-1at0.1,1and2C, respectively, whichwas the highest among the previous reported values. Especially, the α-LiFeO2nanoparticle exhibited improved cycle stability at2C. The capacity retention was around55.2%with the discharge capacity of101.5mA h g-1after50cycles at2C. 4）The electrochemical performance of nanosized α-LiFeO2cathode material usingmicroporous carbon paper(which is first used in the cathode material) or aluminumcurrent collectors was investigated. The results show that nanosized α-LiFeO2electrodeusing microporous carbon paper current collector exhibits much higher dischargecapacity than that using aluminum current collector although the cell reaction mechanismis not dependent on the current collector. Moreover, the rate capacity for the nanosizedα-LiFeO2electrode using microporous carbon paper current collector is extremely high.This may be attributed to the unique structure and excellent electrical conductivity ofmicroporous carbon paper.