Development of a Pasted Nickel Electrode with High Active Material Utilization

Abstract

A high-performance and low-cost pasted nickel electrode made from a metal fiber substrate has been developed. The electrode is designed so that it exhibits active material utilization close to 100%, with an energy density as high as 170 mAh/g or 520 mAh/cm 3. This high active material utilization, even with a metal fiber substrate, which is a poor current collector compared with a conventional sintered nickel powder plaque, has been made possible by adding CoO which dissolves and precipitates on the surface of nickel hydroxide particles as [~-Co(OH)2 during standing and then is converted to CoOOH during the subsequent charging, which provides a good electrical path between the nickel hydroxide particles and the metal fiber substrate. Thus-formed CoOOH is not reduced in the subsequent discharges of the electrode and serves as a good current collector to ensure a high active material utilization throughout the life of the electrode.

Nickel hydroxides and related materials: a review of their structures, synthesis and properties

“…This method has also been called 'dip-coating' [132], a term that also refers to other techniques. Battery electrodes are also prepared by the suspension-impregnation method, in which an Ni(OH) 2 suspension is deposited onto a porous substrate [6,72,[133][134][135]. Ni(OH) 2 may also be deposited onto a substrate by slow precipitation from a single solution [16,136].…”

Structure and electrochemical properties of nickel hydroxide electrodes with cobalt additives

“…1c), which indicates a crystallinity reduction of nickel hydroxide since the crystal defects increase with the substitution of cobalt for nickel in the crystal lattice. On the other hand, as post-added CoO dissolves in the electrolyte, forming a deep blue complex, and then upon the first oxidation b-CoOOH precipitates on the surface of nickel hydroxide particles [1], its structure may be similar to the latter thus the diffraction peaks of the active material (Fig. 1d) shows little change.…”

“…Decrease in R ct and increase in C dl indicate that the surface electrochemical activity of nickel hydroxide can be improved by both incorporated cobalt additives. The effects of post-added CoO are particularly notable since b-CoOOH coated on the surface of nickel hydroxide particles has higher electrical conductivity than NiOOH [1]. Figure 5 shows typical charge-discharge curves of the sealed Ni-MH batteries with different Ni(OH) 2 electrodes.…”

“…In these Ni(OH) 2 electrodes, cobalt hydroxide is currently used as an additive because of its beneficial effects on electrode performance, for example, enhancement of electrode conductivity [1][2][3] and a better chargeability [4][5][6]. Cobalt incorporation to the Ni(OH) 2 electrode is usually realized either by chemical substitution for nickel in the crystal lattice during the Ni(OH) 2 synthesis (e.g., co-precipitation), or by addition of a cobaltbased compound to nickel hydroxide when preparing the admixture to be pasted into a nickel foam (post-addition).…”

Effects of ball milling on the physical and electrochemical characteristics of nickel hydroxide powder

“…In order to improve the cell performance, pasted nickel electrodes made from a porous nickel-foam substrate and an active material called spherical nickel hydroxide powder have been developed. With their high energy density and low cost relative to those of conventional sintered nickel electrodes, the pasted nickel electrodes have now been widely used in commercially available Ni/MH and Ni/ Zn batteries [3][4][5]. The practical importance of nickel hydroxide materials and their electrochemical properties is not only limited to battery application, since nickel hydroxide or nickel oxide electrodes also find important applications in fuel cells, electrochemical capacitors, electrolysers, electrosynthetic cells and electrochromic devices.…”