Phase structure and electrochemical properties of A5B19 La0.8-xPrxMg0.2Ni3.8 (x = 0–0.3) hydrogen storage alloy anode material

Abstract

The La0.8-xPrxMg0.2Ni3.8 (x = 0, 0.05, 0.1, 0.2, 0.3) alloy were synthesized useing the induction melting method. X-ray diffraction, scanning electron microscope, electron probe micro analyzer, and electrochemical tests were used to analyze the structure and electrochemical performance of the La0.8-xPrxMg0.2Ni3.8 (x = 0–0.3) alloy. It was studied how the Pr element affected the electrochemical characteristics and microstructure of the A5B19 La-Mg-Ni based hydrogen storage alloy. The results show that the alloy consists of the CaCu5-LaNi5 phase, 2 H-Pr5Co19 phase, and 3R-Ce5Co19 phase. The abundance of the A5B19 phase increase with the increase of Pr content, while the abundance of the LaNi5 phase decrease, and the addition of Pr promotes the formation of the 2 H-Pr5Co19 phase. According to the results of the electrochemical test, every sample has good activation qualities, and the activation can be completed in 3–4 times. The activation properties are not significantly altered by the addition of Pr. The maximum discharge capacity increases at first, then decreases, reaching the highest 371.15 mAh g−1 at x = 0.2. The cyclic stability gradually improves with increasing content of Pr, and the maximum capacity retention rate reaches 85.80 % after 100 cycles. The primary factor influencing the alloy's high rate discharge ability is the exchange current density. With the increase of the exchange current density, the high rate discharge performance is gradually enhanced.