Sony develops mercury-free alkaline button cell

Sony has developed a new type of alkaline manganese button-cell that contains no mercury and will put it on sale later this year, it said Wednesday.

Alkaline manganese cells are commonly used in cameras, remote controls and calculators and are one of several types of button-cell batteries, so-called because the small, round, metal-cased batteries look similar to buttons.

When not properly disposed of, mercury can contaminate groundwater supplies and enter the food cycle. In sufficient quantities it can cause serious neurological problems, birth defects and death.

A small quantity of mercury is typically used in the batteries to prevent zinc anode erosion, which occurs when it is exposed to the alkaline solution in the battery and results in the creation of hydrogen gas inside the battery. A build-up of hydrogen could cause the battery to rupture and leak, so mercury is typically added to impede erosion of the anode and stop the creation of gas.

In the new battery Sony has added a gas absorbing material into the battery's cathode to compensate for the lack of mercury and prevent a gas build-up, it said.

The mercury-free alkaline manganese button-cell comes four years after Sony developed a mercury-free silver oxide button-cell. Together, those two changes will eliminate 470 kilograms of mercury a year from Sony's battery production.

With the development, Sony is mercury-free in three of its four families of button cells. Mercury is still required in zinc-air batteries, typically used in hearing aids. The remaining type of button-cell, lithium ion, has never contained mercury.

The mercury-free Sony batteries will hit international markets beginning in September and will go on sale in Japan on Oct. 10, Sony said. They will cost around ¥200 (US$2) each in Japan, while overseas pricing has yet to be determined.

IDG News Service

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