The Effect of Gadolinium Ion Doping on Electronic Conductivity of LiFePO₄/C

Abstract

In the recent years, LiFePO4 has been widely developed as a cathode for lithium ion batteries because it has high theoretical capacity (170 mAh/g), good stability and is also environmentally friendly. However, the poor electronic conductivity (~10-9 S/cm) and low diffusion coefficient of lithium ion (~10-15-10-14 cm2/s) are limiting its application. Some solutions to overcome this problem are carbon coating and doping metal ions. This study aims to determine the effect of Gd3+ ion doping on the electronic conductivity of LiFePO4/C. The synthesis method was used is carbothermal reduction with Fe2O3, Gd2O3, LiH2PO4 and carbon black reagents. The synthesized LiFe1-xGdxPO4/C was characterized using XRD, SEM-EDS, and four point probes. The results obtained showed that gadolinium ion doping increased the conductivity of LiFePO4/C from 1.8952 x10-6 to 8.69x10-6 Scm-1 using 0.07 mol ion Gd3+.

The role of metal substitutions in the development of Li batteries, part I: cathodes

“…379 However, Molenda et al 380 observed small increases in conductivity with Al 3+ , Zr 4+ , and W 6+ substitution of 25% atom and recently, a small increase in conductivity (less than one order of magnitude) was observed by gadolinium substitution into LFP. 381 Overall, there is evidence that partial metal substitutions can effectively enhance the electrochemical performance of LFP, specifically increasing the reversible capacity and rate performance, but often at the cost of reduced longterm stability and the particles must be coated with a conductive material to cycle effectively. Complete metal substitution has been shown to yield materials of high theoretical energy densities.…”