Abstract:
LiFePO4 half-cells were fabricated into CR2032 coin-type cells, inside an Argonfilled
glove box using a polypropylene separator and Li metal foil as an anode.
The apparent DLi of LFP cells, were established using three techniques namely
Galvanostatic Intermittent Titration Technique (GITT), Cyclic Voltammetry (CV)
and Electrochemical Impedance Spectroscopy (EIS) technique. These
electrochemical techniques are most extensively used to investigate the diffusion of
Li in the electrode materials of LIBs. GITT profiling of the fabricated cell were
conducted at room temperature via a high precision four quadrant source
measurement unit (SMU) PXIe-4139 by National Instruments. GITT profiling was
carried out at two C-rates for the sake of comparison: 0.1 and 0.5 C. Electrochemical
impedance spectroscopy (EIS) and cyclic voltammetry (CV) were conducted using
an electrochemical workstation model 660E by CH Instruments. CV profile of the
cell was obtained using a potential window of 2.8 to 4.3 V at sweep rates of 0.05,
0.1, 0.2, 0.5, and 1 mVs-1 . Whereas EIS measurements were conducted to obtain Nyquist plot having amplitude of 5 mV at frequency scale of 0.1 Hz – 1 MHz. The
results demonstrate that the accuracy of the estimation of DLi can be enhanced
considerably by an in depth understanding of the electrodes microstructure in
conjunction with a balanced use of these three techniques. The DLi rate acquired
using the GITT technique fell within the order of 10-1. The average DLi values derived by the results of the EIS and CV techniques fell in the order of 10-1. The average DLi
values derived by the results of the EIS and CV techniques fell in the order of 10
–18–192–1–10 cm2s-1.
