Iron-nickel oxide cells

The iron-nickel oxide alkaline battery system has many features in common with the nickel-cadmium system discussed above. It was first developed by Edison in the USA at the turn of the century and was patented in the same year as Jungner s first nickel-cadmium US patent, 1901. Iron can be regarded as a favourable active battery material because of its low cost, high theoretical specific capacity (twice that of cadmium) and non-toxic, pollution-free characteristics. However, because its reduction potential is below that of hydrogen, and since hydrogen overvoltage is low on iron, charge retention is poor and efficiency is low. 

Manufacture of iron-nickel oxide batteries commenced in 1908, but the system did not have the commercial success of nickel-cadmium. Until comparatively recently, there was only a very limited production of stationary batteries in the USA, Germany and Russia. Developments of improved iron electrodes have altered the situation, and the iron-nickel oxide system is now being actively considered for EV propulsion and other applications. 

The cell in fully charged state can be written as Fe(s)lKOH(aq)INiO(OH)(s) 

It is probable that a range of soluble species such as Fe(OH)2 and Fe02 are involved, and it is known that Fe(OH)3 or Fe304 may be formed on deep discharge. The practical energy density of conventional tubular plate cells is 20-30 Wh/kg with the more recent cells which use press-sintered iron electrodes, values of 40-60 Wh/kg have been reported. 

Recently, cells employing thick sintered nickel plates on nickel-plated porous steel substrates have been developed which have greatly improved energy densities. The active material is introduced by electroprecipitation. Electrodes based on nickel fibre supports are also being studied. 

---

Iron-nickel oxide cells are always vented. Tubular/pocket plate electrodes are constructed as described above and are generally housed in nickel-plated steel cases. Cells with sintered plate electrodes have smaller inter-electrode spacings. They use synthetic fibre fabrics as separators, and plastic containers. 

Fig, 6.20 Discharge (a) and charge (b) characteristics of a typical iron-nickel oxide cell ai C/3, as a function of percentage capacity... 

Hybinette A process for extracting nickel from sulfide ores. The nickel ore that occurs in Canada is a mixture of the sulfides of nickel, copper, and iron. Several methods have been used to separate these metals. In the Hybinette process, the ore is first smelted in a blast furnace, yielding a nickel-copper matte (i.e., a mixture of their lower sulfides). This is roasted to remove sulfur and leached with dilute sulfuric acid to remove copper. The resulting crude nickel oxide is used as the anode of an electrochemical cell. The nickel deposits on the cathode, which is contained in a cloth bag. Precious metals collect in the anode slime. The process was invented by N. V Hybinette in 1904 and operated at the Kristiansand refinery, Norway, from 1910. 

Nickel(lll) oxide, prepared from a nickel(ii) salt and sodium hypochlorite, is used for the oxidation of alkanols in aqueous alkali [46]. Residual nickel(Ii) oxide can be re-activated by reaction with sodium hypochlorite. Nickel oxides have also long been used in the manufacture of the positive pole in the Edison nickel-iron rechargeable battery, now largely superseded by die lead-acid accumulator, and in the Jungner nickel-cadmium batteries used as button cells for calculators [47]. Here, prepared nickel oxide is pressed into a holding plate of perforated nickel. Such prepared plates of nickel(lli) oxide have been proposed as reagent for the oxidation, in alkaline solution, of secondary alcohols to ketones and primary alcohols to carboxylic acids [48]. Used plates can be regenerated by anodic oxidation. 

The Edison cell uses an iron anode, nickel oxide eathode, and KOH electrolyte. This cell is extremely rugged and is still used in certain industrial apphcations, but it was never able to displace the lead-acid cell as Edison had hoped.. 

In alkaline solution nickelous hydroxide can be oxidized to n hydrated nickelic oxide, NiOo xHoO. This reaction is used in tin Edison storage cell. The electrodes of this cell are plates coated will Ni0.2 xHoO and metallic iron, which are converted on discharge of tlu cell into nickelous hydroxide and ferrous hydroxide, respectively. Tht electrolyte in this cell is a solution of sodium hydroxide. 

INCO produced electrolytic nickel at its refinery in Port Colborne, Ontario, Canada. The production started in 1926. The anodes were made by reducing nickel oxide with coke, and the anodes contained about 93.5% Ni, 4% Cu, and 1% Co. The sulfur content was low, about 0.6%. The approximate composition of the purified electrolyte was 60 g L-1 Ni2+, 95 g L-1 S042-, 35 g L-1 Na+, 55 g L-1 Cl , and 16 g L 1 boric acid, and the temperature was 60 °C. The current density of the process was 16 A/sq.ft (approximately 170 A m-2) and the cell voltage was about 1.6 V. At the normal cell operating voltage, the principal impurities - iron, cobalt, lead, arsenic, and copper - dissolved into the solution with nickel. Silver, gold, the PGMs, sulfur, selenium, and tellurium fell to the bottom of the cell as an insoluble slime. The produced cathodes... 

Table 4. Component Data and Energy Density for 300 A h Nickel Oxide—Iron Cells...

---