Microstructure and Electrochemical Properties of La<sub>0.35</sub>Ce<sub>0.65</sub>Ni<sub>3.8-X</sub>Co<sub>0.8</sub>Mn<sub>x</sub>Al<sub>0.4</sub> Hydrogen Storage Alloys

Abstract

Microstructure and electrochemical characteristics of La0.35Ce0.65Ni3.8-xCo0.8MnxAl0.4 alloys have been investigated. X-ray diffraction results indicate that the alloys consist of a single phase with CaCu5-type structure, and the lattice parameters a, c and cell volume V increase with increasing x value. The maximum discharge capacity of the alloy electrodes first increases from 217.9 (x = 0) to 290.1 mAh/g (x = 0.3), and then decreases to 271.3 mAh/g (x = 0.5). The high-rate dischargeability at the discharge current density of 1200 mA/g first increases from 58.4% (x = 0) to 78.2% (x = 0.3), and then decreases to 75.2% (x = 0.5). Both the charge-transfer reaction at the electrode/electrolyte interface and the hydrogen diffusion in the bulky alloys are responsible for the high-rate dischargeability. Cycling stability first increases with increasing x from 0 to 0.3 and then decreases when x increases to 0.5.