A method for the manufacturing of metal hydride alloy powders with fast reaction kinetics and improved initial activation behaviour has been developed. The activated MH powders can be discharged with current densities higher than 2 A/g to 80% of their maximum capacity. Maximum discharge capacities are available after only a view activation cycles.
The limiting steps for metal hydride alloy respectively metal hydride electrode kinetics have been identified as surface reactions on the metal hydride. Metal hydrides with remarkably improved surface activity have been manufactured in laboratory scale. On the basis of these investigations an up-scaled process for powder production has been developed. In parallel the influence of the electrode and cell design on battery kinetics have been investigated. Electrode manufacturing, additives, current collector etc. have been optimised.
The metal hydride electrodes developed under this project can be used as negative electrodes in alkaline batteries for industrial applications, substituting the state-of the art cadmium electrodes. Moreover, these electrodes are characterised by the high power capability (discharges up to 10 C) according to the alloy performance and the other electrode components: nickel fibre substrate, active material formulation and electrode preparation procedures.
With the improved electrode materials and battery manufacturing techniques prototype batteries have been manufactured and successfully tested in standard test equipment as well as in application tests. In deep discharge cycling 80% of the battery capacity was available at 10C discharge rate. The measured maximum specific power has been about 600 W/kg.
Objectives and content
Since 1991, Nickel-Metal Hydride rechargeable batteries as an alternative to Nickel-Cadmium batteries have been very successful for consumer applications with low discharge rates and long cyclic stability (e.g. mobile phones). The main advantages of Ni-MH batteries are their higher energy capacity, theelimination of the memory effect and the absence of toxic Cadmium when compared to the corresponding NiCd battery.
The aim of this project is a lasting increase of electrochemical reaction kinetics inside the Ni-MH battery by studying the reaction limiting processes both in the metal hydride alloy and at the metal hydride/electrolyte interface. Based on these results new fast kinetics metal hydride alloys will be developed and manufactured as well as the corresponding metal hydride electrodes and cells with high power performance.
The combination of both the general advantages of the Ni-MH battery and the high power performance will lead to a new battery generation which will be able to fulfil the demands of cordless tool and electric vehicle applications.
The consortium comprises research groups on solid state physics and electrochemistry of Universities (Fribourg, Salford, Stockholm) and a research centre (CNRS), a manufacturer of metal hydride alloys (GfE), battery manufacturers (Leclanché, NIME, Tudor) and an end user (Electrolux).
Funding SchemeCSC - Cost-sharing contracts
383 22 Mönsteras
19200 Azuqueca De Henares
106 91 Stockholm
M5 4WT Salford