• Transactions of the Korean hydrogen and new energy society
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• v.7 no.2
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• pp.157-164
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• 1996

The AB5-type metal hydride electrodes using $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$(LM : Lanthaniumrich Mischmetal) alloy powders(${\leq}200$mesh) which were coated with 25wt% copper in an acidic bath were prepared with or without addition of 10wt% PTFE as a binder. Prior to electrochemical measurements, the electrodes were sintered at $40^{\circ}C$ for 1 and 2hrs in vacuum with Mm(mischmetal) and sponge type Ti getters. The properties such as maximum capacity, cycle life and mechanical strength of the negative electrode have been investigated. The surface analysis of the electrode was also obtained before and after charge-discharge cycling using scanning electron microscope(SEM). From the observations of electrochemical behavior, it was found that the sintered electrode shows a lower maximum discharge capacity compared with non-sintered electrode but it shows a better cycle life. For the both electrodes with or without addition of PTFE binder, the values of mechanical strength were obtained, and their values increased with increasing sintering time. However, there is little difference of discharge capacity for both electrodes.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.1
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• pp.29-38
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• 2001

The alloys $ZrMn_2Ni_x$ (x=0.0, 0.3, 0.6, 0.9 and 1.2) as the alloys of Zr-Mn-Ni three component system were prepared and their hydrogen-storage properties and their electrochemical properties were investigated. The C14 Laves phase formed in all the alloys $ZrMn_2Ni_x$. Among these alloys $ZrMn_2Ni_{0.6}$ was activated relatively easily(after about 11 charge-discharge cycles), and had the largest discharge capacity(max. 45mAh/g). For all the alloys Zr was dissolved most easily into the 6M KOH solution. More Mn and Ni were dissolved from the $ZrMn_2Ni_{0.6}$ alloy than from the other alloys. Due to the active charge and discharge of the $ZrMn_2Ni_{0.6}$ alloys, related to the easier activation and the larger discharge capacity, Zr, Mn and Ni in this alloy were considered to be dissolved more easily into the 6M KOH solution, compared with the other alloys.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.4
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• pp.135-141
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• 1998

The effects of heat-treatment on discharge characteristics of $TiFe_{1-x}Ni_x$ alloy were investigated. The content of Ni in alloy was varied from x = 0.1 to 0.6 by each 0.1 increment. Discharge capacity change of each alloy with C/D cycles was measured. With increasing Ni-content initial discharge capacity was increased. but at x = 0.6 it was deceased again. With increasing C/D cycles discharge capacity was rapidly decreased in the alloy of high Ni-content. In order to investigate the effects of heat-treatment on cycle life, $TiFe_{0.5}Ni_{0.5}$ alloy having maximum initial discharge capacity was heat-treated at various temperatures in the range of $700{\sim}900^{\circ}C$ and tested. The loss of initial discharge capacity was appeared at all temperatures. but cycle characteristics of the alloy was improved. The electrodes heat-treated for 1 hour in the range of $700{\sim}850^{\circ}C$ showed good recovery of discharge capacities through repeated cycles, and from SEM observation results these were considered as 1 hour in the range of $700{\sim}850^{\circ}C$ showed good recovery of discharge capacities through repeated cycles, and from SEM observation results these were considered asbeing due to increased electrode strength and small loss of porosity during heat-treatment. The electrode heat-treated for 1 hour at $900^{\circ}C$ showed poor discharge characteristics because of low porosity.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.4
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• pp.161-167
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• 1998

It has been investigated the effects of alloying elements and binders on the corrosion behavior of metal hydride electrodes for anode of Ni/MH secondary battery. The $AB_5$-type alloys, $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$ and $(LM)Ni_{3.6}Co_{0.7}Mn_{0.3}Al_{0.4}$, were used for the experiments. The electrodes were prepared by mixing and cold-pressing of alloy powders with Si sealent or PTFE powders, or cold-pressing the electroless copper coated alloy powders. The amount of copper coating was 20wt%. In order to examine corrosion behavior of the electrodes, the corrosion current and the current density, in 6M KOH aqueous solution after removal of oxygen in the solution, were measured by potentiodynamic and cyclic voltamo methods. The results showed that Co in the alloy increased corrosion resistance of the electrode whereas Ni decreased the stability of the electrode during the charge-discharge cycles. The electrode used Si sealant as a binder showed a lower corrosion current density than the electrode used PTFE and the electrode used Cu-coated alloy powders showed the best corrosion resistance.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.2
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• pp.141-149
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• 1999

Recently the Ni/MH secondary battery has been studied extensively to achieve higher energy density, longer cycle life and faster charging-discharging rate etc. In this work, the electrode properties of $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$ alloy and $Ti_{0.6}Zr_{0.4}V_{0.6}Ni_{1.4}$ alloy with addition of Pd were investigated. These alloys did not show any change in XRD pattern by Pd addition. As Pd was added as alloy element, the activation behavior was not affected significantly in both $AB_2$ type and $AB_5$ type electrodes and, On charging and discharging in high current density, Discharge capacity with increasing of Pd content was more decreased. But cycle life was showed increasing. Especially the electrode of $Ti_{0.6}Zr_{0.4}V_{0.6}Ni_{1.4}+0.5wt%$ Pd alloy was not almost decreased discharge capacity for 400cycles.