Electrochemical property investigation of cobalt doped LiFePO4/C during charge-discharge by an in-situ x-ray near edge structure technique

Abstract

LiFePO4/C and LiFe0.9Co0.1PO4/C materials were synthesized via a solid state method. 10% cobalt was chosen as a doping element in the Fe-site of LiFePO4/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 LiFe0.9Co0.1PO4/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 LiFe0.9Co0.1PO4/C mainly took place with the Fe2+/Fe3+ redox couple. The Co2+/Co3+ couple redox was not active during cycling. The Co doped sample had an improved crystal structure, resulting in a higher energy density than LiFePO4/C.