Failure Mechanisms of Nickel/Metal Hydride Batteries with Cobalt-Substituted Superlattice Hydrogen-Absorbing Alloy Anodes at 50 °C
The incorporation of a small amount of Co in the A2B7 superlattice hydrogen absorbing alloy (HAA) can benefit its electrochemical cycle life performance at both room temperature (RT) and 50 °C. The electrochemical properties of the Co-substituted A2B7 and the failure mechanisms of cells using such alloys cycled at RT have been reported previously. In this paper, the failure mechanisms of the same alloys cycled at 50 °C are reported. Compared to that at RT, the trend of the cycle life at 50 °C versus the Co content in the Co-substituted A2B7 HAAs is similar, but the cycle life is significantly shorter. Failure analysis of the cells at 50 °C was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), and inductively coupled plasma (ICP) analysis. It was found that the elevated temperature accelerates electrolyte dry-out and the deterioration (both pulverization and oxidation) of the A2B7 negative electrode, which are major causes of cell failure when cycling at 50 °C. Cells from HAA with higher Co-content also showed micro-shortage in the separator from the debris of the corrosion of the negative electrode.
Degradation mechanisms of high-energy bipolar nickel metal hydride battery with AB5 and A2B7 alloys
Abstract The failure modes of nickel/metal hydride batteries made from conventional AB 5 and La-only Mg-containing A 2 B 7 metal hydride alloys were studied at the end of 70% state-of-charge cycle life testing (reaching below 3.1 Ah capacity in a 5.5 Ah design cell) by the combination of inductively coupled plasma, scanning electron microscope, X-ray energy dispersive spectroscopy and composition mapping, and X-ray diffraction analysis. The capacity degradation of cell with AB 5 alloy was found to have been caused by the combination of metal hydride alloy oxidation and non-reversible γ-NiOOH phase formation, which was promoted by the incorporation of Al leached out from the oxidation product of the Al-containing negative electrode. In the cell with Al-free A 2 B 7 alloy, the end of cycle life was the result of pulverization in the main A 2 B 7 phase.
A New Vacuum Pressure Infiltration CFRP Method and Preparation Experimental Study of Composite
In order to prepare a carbon-fiber-reinforced polymer composite (CFRP) with ideal microstructure and properties, a new vacuum pressure infiltration CFRP method is proposed based on an analysis of existing CFRP preparation process methods. Research on composite material preparation systems was carried out by using this new method principle. The system mainly includes a fiber pre-forming module, a vacuum heating infiltration module, a hot-press curing molding module, and a data acquisition control module. Under the conditions of natural curing at 0 MPa + 6 h + 25 °C, vacuum heating curing at –0.05 MPa + 30 min + 80 °C, and hot-press curing at 0.7 MPa + 5 min + 50 °C, a two-dimensional (2D) CFRP with excellent microstructure and properties was successfully prepared. Observing the microstructure of the prepared composite material, it can be found that the inside of the composite material was sufficiently and uniformly infiltrated, and common preparation defects such as holes and delamination were effectively controlled. Through the performance test, the bending strength of the material reached 790 MPa.