Effects of Carbon Crystallinity on Hydriding-Dehydriding and Charge-Discharge Characteristics of MgNi Alloy-Carbon Material Composites

Abstract

Hydriding-dehydriding and charge-discharge characteristics of amorphous MgNi alloys modified by ball-milling with different carbon materials were investigated with the intention of using them in nickel-metal hydride batteries. It was found that the ball-milling with carbon materials markedly improved hydriding-dehydriding and charge-discharge characteristics of the MgNi alloy, and an optimum ball-milling time was shortened by utilization of carbon material with lower crystallinity. However, ball-milling for longer than the optimum time led to a decrease in the amount of absorbed hydrogen and the discharge capacity, which was ascribed to the formation of MgNi 3 C. These results indicate that the characteristics of MgNi alloy-carbon material composites greatly depend on both crystallinity of carbon material used and ball-milling time.

Effect of Ni Content on Rate Capability of Mg[sub 0.9]Ti[sub 0.06]V[sub 0.04]Ni[sub x] Negative Electrodes for Nickel/Metal Hydride Batteries

“…One is bulk modification, that is partial substitution of constituent elements with foreign metals, [8][9][10][11][12][13][14][15][16][17][18] and another is surface modification. [19][20][21] We have found that the discharge capacity was increased by surface modification, i.e., ballmilling of MgNi with carbon materials such as graphite, Ketjen black, etc., [22][23][24][25][26] while cycle performance was improved by bulk modification, i.e., partial substitution of Mg in a MgNi alloy with Ti and/or V in the ballmilling. 24,25,27 It was concluded that the Mg 0.9 Ti 0.06 V 0.04 Ni alloy was the most appropriate composition from the viewpoint of both discharge capacity and cycle performance.…”

An Industrial-Based Consortium to Develop Premium Carbon Products from Coal Final Report - Part 2

“…18 Ball milling of carbon materials has been used as a strategy to produce carbon-based hydrogen storage materials, [19][20][21][22] and carbon-metal hydrogen storage composites. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] The performance of ball milled carbon composites is generally a function of ball-milling time, the presence of a solvent during processing, [23][24][25][26][27] and the breakdown of the graphitic structure. 25,31,38 Graphitic carbon becomes rapidly amorphitized during milling, evidenced by a rapid decrease in the characteristic graphite 002 (2θ=26º) reflection in X-ray diffraction (XRD).…”

“…28 The effect of temperature on cumulative pore volume and cumulative surface area of pyrolyzed Red Hills lignite…”

Influence of Zr Addition on Structure and Performance of Rare Earth Mg-Based Alloys as Anodes in Ni/MH Battery

“…However, the lower theoretical discharge capacity impedes their practical application. Subsequently, Zr-based or Ti-based alloys [4], V-based solid solution alloys [5] and Mg-based amorphous alloys [6,7] were extensively studied. However, Ti-based or Zr-based anodes need too many charge/discharge cycles to achieve their maximum discharge capacities, while Mg-based anodes quickly lose their discharge capacities because of the corrosion of Mg in KOH electrolyte [8][9][10][11].…”