Enhancing the life of rechargeable NiMH batteries

Researchers at Stockholm University have developed a method to multiply the lifespan of nickel-metal hydride batteries. The new method also means that the batteries can easily be restored once they have begun to wear out, unlike other rechargeable batteries that must be melted down for recycling.

Most rechargeable batteries are based on either lead, nickel-cadmium (NiCd) or various combinations with lithium. Batteries based on nickel-metal hydride (NiMH) with an aqueous electrolyte are both eco-friendly and safe. The NiMH battery is developed from the nickel-hydrogen battery (NiH2). It has long been known that (NiH2) batteries have a superior lifespan compared to other battery types. The inspiration for the new technology came from a new NiMH battery manufactured by Nilar AB in Gävle.

In a NiMH battery, hydrogen is bound in the metal alloy. This solution is effective, but the battery ages because it dries out as the alloy slowly corrodes and consumes its water-based electrolyte. The corrosion also interferes with the internal balance between the electrodes in the battery. The breakthrough came when the research group discovered that they could counteract the aging process almost completely by adding oxygen, which restores the lost electrode equilibrium and replaces the lost electrolyte. With the right balance of oxygen and hydrogen, a lifespan is achieved which exceeds all of today’s common battery types.

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