|Ni Foam (Fraunhofer)|
The nickel foam will be used to produce electrodes for batteries destined for hybrid vehicles and other consumer items. The Dalian venture will produce 2 million square metres of nickel foam a year, about half of Inco’s annual global output of the product.
Inco, Korea Nickel Corporation and Liaoning Wanzhong Real Property Development of Dalian have invested a total of US$ 25 million in the joint venture. Inco has a controlling stake of 77%, Korea Nickel 20% and the Chinese partner 3%.
Inco, the world’s second largest producer of nickel, has recently grown to become the world’s leading supplier of nickel foam. Earlier this year, the company acquired the nickel foam assets of Shenyang Golden Champower, one of China’s leading nickel foam manufacturers. Inco also manufactures nickel foam at its refinery in Clydach, Wales.
Including the new joint venture, Inco’s total investment in China has risen to US $80 million.
The Dalian plant will use indigenous electroplating technology licensed from China’s Harbin Institute of Technology.
Our Dalian technology is arguably the best in the world for making this type of nickel foam. It provides an ideal complement to the carbonyl technology we use at Clydach, which produces foam products with different characteristics.
Our venture in Dalian and our recent acquisition of Golden Champower are consistent with our strong belief that China will continue to drive world nickel demand. We want to ensure we remain China’s nickel market leader, and we will keep looking for new opportunities to expand our presence in China.—Peter Goudie, Inco Executive Vice-President
There are two primary commercial technologies for manufacturing nickel electrodes (which have been in existence for some 100 years): sintering and pasting.
Sintering describes a process in which a metallic powder is heated without melting to form a coherent mass.
A sintered electrode consists of a substrate, a porous Ni plaque sintered on the substrate, and an active mass of Ni(OH)2 filled in the pores of the plaque. Sintered electrodes are characterized by high rate capability, good longevity, long-term storage, and low self-discharge. The electrode is widely used in portable NiCd and NiMH batteries and is highly preferred for high drain-rate applications.
Pasted electrodes, however, are gaining in popularity due to reduced complexity in mass production, higher specific capacity, and lower environmental concerns. The performance of NiMH batteries using pasted nickel electrodes has advanced quickly and even the power density is approaching and outperforming those with sinter electrodes.
A pasted electrode is made by pasting a slurry of active mass that contains Ni(OH)2, additives and binder materials into a porous nickel foam, followed by drying and calendaring to finish the electrode.
And in turn, there are two primary commercial processes for the mass-production of continuous sheets of nickel foam: electroplating or chemical vapor deposition.
The Clydach carbonyl process, developed by Inco and commercialized in 1999, is a chemical vapor deposition process. It uses the unique properties of the reaction between carbon monoxide and nickel to plate a polyurethane foam substrate with nickel.
Carbon monoxide reacts with nickel at about 80ºC to form gaseous nickel carbonyl. This gas decomposes back to nickel metal and carbon monoxide when heated to about 150ºC.
Inco passes polyurethane foam through an atmosphere of nickel carbonyl and then heats the polyurethane with infra-red heaters, decomposing the nickel carbonyl back to nickel on the surface of the polyurethane.
The nickel-coated polyurethane substance is then heat-treated in a high-temperature furnace to burn out the polyurethane substrate and to anneal the nickel. The result is a nickel foam.
The advantage of the carbonyl process is that it produces an exceptionally uniformly-plated product that is highly porous and pliable. The vapor deposition process also results in the generation of less hazardous waste when compared to electroplating.
Electroplated foam requires first that the polyurethane foam substrate is made electrically conductive. The foam is then plated in a nickel bath in an analogous manner to typical electroplating of parts for corrosion resistance or decorative purposes. (Chrome plating includes a layer or layers of plated nickel followed by a chromium layer). This electroplated foam is then subjected to a similar high temperature furnacing as for carbonyl foam.
Electroplated nickel foam tends to have an uneven distribution of nickel, with thicker Ni strands near surface and weaker stands in the middle due to the edge effect of current distribution during electroplating.
Inco researchers are exploring the use of using Ni filaments in the active mass to create a secondary conductivity network within the Ni foam cells. The secondary conductivity network created by the addition of these filaments might offset the large pore size characteristic of nickel foam (that usually requires additional and costly steps such as pre-compression or the use of conductivity additives such as cobalt) and the uneven distribution of nickel characteristic of the electroplating process.
Both results could result in lower-cost, higher-quality nickel foams.
Pasted Ni(OH)2 Electrodes using INCO Ni Powders For High Drain Rate Ni-based Batteries, Journal of The Electrochemical Society, April 2003, Vol. 150, Issue 4, pp. A543-A550
CVD Technique for Inco Nickel Foam Production, Advanced Engineering Materials, 2004, Vol. 6, Issue 6, Pages 454 - 459