Surface Modification And High-Temperature Electrochemical Performance Of Perovskite-Type Oxide LaFeO₃

Perovskite-type oxide LaFeO3 is a novel negative matieral for metal hydride-nickel(MH-Ni) batteries. However, several inherent drawbacks, such as the intrinsical poor conductivity and nanosized particles’ easy aggregation, are becoming its performance-limiting factors. To overcome the mentioned obstacles, polyaniline(PANI)-treatments, carbon-treatments and carbon/PANI combined treatments were applied to improve the high-temperature electrochemical performance of LaFeO3 at 60 oC. The micromorphology characterization was performed by FE-SEM, TEM and FT-IR methods. Electrochemical kinetic parameters of LaFeO3 electrode at 60 oC were also systematically measured.After PANI treatments, PANI layers appeared uniformly on the surface of LaFeO3 particles. Owing to the PANI layers, at an elevated temperature(60 oC), the maximum discharge capacity(Cmax) of the LaFeO3 electrodes remarkably increased from 234 m Ah/g to 346 m Ah/g and charge retention(CR) increased from 85.4% to 94.6%. Also, the high rate dischargeability of LaFeO3 electrodes at a discharge current density of 1500 m A/g(HRD1500) increased from 23.8% to 41.8%.Carbon-coated LaFeO3 composites were obtained using the PANI pyrolysis method. Results revealed that LaFeO3 particles were evenly coated with carbon layers. The carbon layers could enhance the conductivity and electrocatalytic activity, speeding up hydrogen protons transferring from electrolyte to electrode interface. Furthermore, the carbon coatings hindered the LaFeO3 particles from aggregating into stacks and suppressed the corrosion of the LaFeO3 electrodes. At an elevated temperature(60 oC), owing to the carbon coatings, Cmax of the LaFeO3 electrodes remarkably increased from 211 m Ah/g to 358 m Ah/g and the capacity retention rate after 100 cycles S100 increased from 63.0% to 70.9%. Moreover, HRD1500 of the LaFeO3 electrodes increased from 21.0% to 37.6%.An efficient carbon/polyaniline(PANI)-coated technique was applied for perovskite-type oxide LaFeO3 to enhance its high-temperature electrochemical performance. LaFeO3 particles were evenly coated with carbon and PANI hybrid layers. The cooperation of carbon and PANI hybrid layers resulted in the significant enhancement of high-temperature electrochemical performance. At an elevated temperature(60 oC), owing to the hydrid coatings, the Cmax of the LaFeO3 electrodes remarkably increased from 231 m Ah/g to 402 m Ah/g and S100 increased from 67.1% to 77.6%. HRD1500 of the LaFeO3 electrode increased from 22.7% to 44.3%.