- Several major scientific results were achieved about the influence of both composition and metallurgy on cycling stability and corrosion resistance of AB5 alloys;
- Among all the compositions tested, two of them seems promising for an industrial application because of a higher energy storage capacity (about 10% increase of capacity), a lower Co content (7% w/w) and therefore a lower cost than the initial reference alloy. Metallurgical processes (cooling technique, annealing treatment) were tuned in order to obtain a comparable or a higher cycling stability. Prototype evaluation confirmed the higher capacity (+ 4.6%) and the comparable cycle life of the batteries manufactured with one of the new developed alloys;
- The other one exhibited a lower corrosion rate (- 18%) under storage at high temperature and could be of interest for standby applications;
- Addition of small amounts of special elements yielded in an improvement of the corrosion behaviour of the alloys which was also confirmed by prototype evaluation;
- Different surface treatment methods like etching and coating procedures were evaluated during the period of this project to improve the properties of the alloys. Although no surface treatment showed an improvement regarding the corrosion behaviour alloy activation and low temperature behaviour could be improved significantly;
- Many different characterisation methods were applied to get detailed information on the metallurgical and electrochemical properties of the alloys to be able to find appropriate correlation and trends which are useful for future alloy and battery development of the industrial partners;
- Detailed surface analyses improved the understanding of the corrosion mechanism on the surface of the alloys;
- Various electrochemical methods were evaluated to find a method to allow rapid alloy characterisation and to predict cycle behaviour. Some methods have the ability to give a rapid overview on some interesting properties of the alloys. They showed some interesting correlation with the results out of the cycling tests but could not be developed so far during project time that e.g. cycle tests can be avoided. After some further improvement of these methods they will have the capability to exhibit a rapid overview of hydrogen storage alloys to be further tested.
Objectives and content
Because it is non polluting, has higher energy storage
capabilities than nickel-cadmium at reasonable cost and
does not show any safety issue, nickel-metal hydride (NiMH) electrochemical system becomes predominant for
portable appliances and is also expected to be the energy
source which will allow electric vehicles (EVs) to become
an industrial reality.
The key component for Ni-MH is an intermetallic material,
a so-called AB5 hydrogen storage alloy with quite complex
chemical composition and metallurgical structure.
The purpose of this programme is to find and optimise
critical parameters which will make possible mass
production of high performance, corrosion resistant and
low cost hydrogen storage alloys.
The proposed research work is focused on:
adaptation of suitable alloy compositions.
development of associated metallurgical processes and
chemical surface treatments.
prototype assembly and electrical tests.
In this programme, two companies which are the Europe's
leaders for MH alloys and batteries are associated. The
partnership also comprises a company which has a wellknown background in the area of chemical surface
treatments related to electrochemical products and
another with an expertise in surface chemical analysis.
In order to be conclusive at short notice, support will
be found in the results of previous EC granted projects
(e.g. cost reduction or kinetics improvements programmes)
and all the work will be concentrated on 30 months.
This project will enable the industrial companies
involved in the programme, as well as other European
battery makers, to become more competitive in two sectors
of the Ni-MH battery business, portable
telecommunications and electric vehicles. Spin-off
effects are also expected in the areas of video, tooling
and emergency lighting technologies. Both European and
American markets are within their reach. An other target
is to consolidate the expertise of some laboratories in
the area of battery related materials.
Funding SchemeCSC - Cost-sharing contracts
ST4 7LQ Stoke On Trent