Luo Shaohua

Synthesis and performance of carbon-modified LiFePO4 using an in situ PVA pyrolysis procedure

LiFePO4/carbon composite cathode material was prepared by granulating and subsequent pyrolysis processing in N2 atmosphere with polyvinyl alcohol (PVA) as the carbon source. The influences of carbon content on the microstructure and battery performance were investigated. Single LiFePO4 phase and amorphous carbon can be found in the products. A special micro-morphology of the optimum sample was observed. The discharge capacity of the cell with the optimum cathode was 135 mAh.g−1, close to the charge capacity of 153 mAh.g−1 at 17 mA.g−1. The influence of ambient temperature on the cell capacity was investigated. The temperature dependence of its electrochemical characteristic was evaluated by using AC impedance spectroscopy. A new equivalent circuit based on the charge and mass transfer control process in an electrode was proposed to fit the obtained AC impedance spectra. The tendency of every element in the equivalent circuit was used to interpret the temperature dependence of the capacity of the optimum cathode.

Electrochemical Performance of Li4Ti5O12 Synthesized by a PVP Combustion Assisted Sol-gel Method

Abstract Li4Ti5O12 samples were synthesized via a PVP (polyvinylpyrrolidone) assisted gel-combustion method by varying the calcination temperature. The effect of different roasting temperatures on the structure, the morphology, and the electrochemical performance of the Li4Ti5O12 material was analyzed. The cycle performance, the structure and the morphology of the prepared material were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and charge/discharge test system. The results show that the Li4Ti5O12 powder has a single-phase spinel structure with uniform particles size. The average particle size is 500 nm. The Li4Ti5O12 material synthesized at 800 oC for 8 h possesses excellent performance, and its first discharge capacity is 167.4 mAh/g.