Effects of Cr addition on the microstructures and electrochemical performances of La–Mg–Ni system (PuNi 3-type) hydrogen storage alloy

Abstract

In order to improve the electrochemical cycle stability of La–Mg–Ni system (PuNi 3-type) hydrogen storage alloy, a trace of Cr was added in the alloy and La 2Mg(Ni 0.85Co 0.15) 9Cr x ( x = 0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of Cr addition on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The obtained results show that Cr addition engenders an inappreciable influence on the phase composition of the as-cast and quenched alloys, but it changes the phase abundance of the alloys significant. The Cr addition markedly enhances the cycle stability of the as-cast and quenched alloys, but it decreases the discharge capacity. When Cr content increased from 0 to 0.4, the discharge capacity of the as-cast alloy decreased from 396.3 to 355.6 mAh/g, and the cycle life prolonged from 72 to 97 cycles. For the as-quenched (30 m/s) alloys, the discharge capacity reduced from 364.2 to 334.2 mAh/g, and the cycle life extended from 100 to 131 cycles.