Electrochemical Property Investigation of Cobalt Doped LiFePO_4/C during Charge-Discharge by an In-situ X-Ray Near Edge Structure Technique

摘要

LiFePO_4/C and LiFe_(0.9)Co_(0.1)PO_4/C materials were synthesized via a solid state method. 10% cobalt was chosen as a doping element in the Fe-site of LiFePO_4/C to increase its electronic conductivity. The crystal structure and particle morphology of this material were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. The electrochemical mechanism observed during cycling of a LiFe_(0.9)Co_(0.1)PO_4/C electrode was investigated using in-situ time resolved X-ray absorption near edge structure (in-situ XANES). The experimental results showed that the electrochemical mechanism of LiFe_(0.9)Co_(0.1)PO_4/C mainly took place with the Fe~(2+)/Fe~(3+) redox couple. The Co~(2+)/Co~(3+) couple redox was not active during cycling. The Co doped sample had an improved crystal structure, resulting in a higher energy density than LiFePO_4/C.