World's first commercialization of Mercury-Free Silver Oxide Battery

September 29, 2004
Sony Mercury Free Silver Oxide Battery, SR626SW

Sony Corporation today announced the accomplishment of the world's first Mercury-free silver oxide battery, which was considered difficult within the industry. Starting January 2005, 10 models of mercury-free batteries will be commercialized on a world-wide basis.

Sony is producing Silver Oxide batteries of all sizes and currently Sony has the top market share. Silver Oxide battery is mainly used for wrist watches, small-size thermometers and mobile game products. Sony started its Silver Oxide battery business in 1977 and, as of September this year (2004), Sony has realized in producing 5 billion cells of Silver Oxide battery cumulatively.

The mercury-freeing technology development announced this time will very much influence the increasing interest of the effect that mercury incorporate in batteries has on environmental issues. Currently, revisions in the battery directives are being made in the European Parliament and European Environmental Council, however it is expected that freeing mercury from silver oxide batteries will be an exception, due to the difficulty in realizing it. However, the new Sony's 0% mercury silver oxide battery made this possible.

Annually, Sony sells approx. 400 Million Silver Oxide batteries worldwide, and considering the fact that the mercury level of Sony's silver oxide batteries is 0.2% of the total content of a battery, making them mercury-free will lead to reducing the annual usage of mercury by 320 kg, which dramatically contribute to protecting the environment.

Also, in the European battery directives, the determinations on the regulation of the level of lead is also under discussion (i.e. to be less than 40ppm), and it should be emphasized that in Sony Mercury-free silver oxide batteries usage of lead has also been eliminated.

The function of Mercury in Silver Oxide Battery

Silver Oxide battery is a small-sized primary battery using Zinc as the negative electrode (anode), Silver Oxide as the positive electrode (cathode) plus an alkaline electrolyte (Fig. 1).

Fig. 1. Schematic Diagram of Silver Oxide Battery Cell
Fig. 1. Schematic Diagram of Silver Oxide Battery Cell

Zinc which is the activator in the negative electrode will corrode in alkaline solution and it is consumed. When this happens, it becomes difficult to maintain the capacity of the unused battery. This corrosion of Zinc also causes electrolysis in the electrolyte and brings about the production of Hydrogen gas, which will result in ascent of inner pressure and expansion of the cell. And for this reason, mercury which suppressed the corrosion of Zinc was added in the battery, however it was desired for mercury to be reduced, for its considerable harm to the environment.

Counter measures to realizing a Mercury-free Silver Oxide Battery

With the below explained three technical countermeasures, Sony has succeeded in preventing the Zinc corrosion (i.e. Hydrogen gas generation), which is indispensable for the achievement of Mercury-free Silver Oxide battery.

1. Adoption of high quality Zinc alloy powder with improved corrosion resistance
By optimizing the mixed ratio of fine metal used (i.e. Zinc-alloy powder), it has been managed to dramatically reduce the corrosion rate, 10 times less, compared to conventional material.

2. Addition of anti-corrosion material into anode materials
This additive can prevent the generation of Hydrogen gas by blocking the gas-generation spots. This leads to reducing the corrosion rate by a half, thus reducing the Hydrogen gas generation dramatically.

3. Adoption of anti-corrosion technology to the collector materials
Suppressing the corrosion of the collector electrode has an effect of suppressing the corrosion of Zinc as well, however on the other hand, if not processed properly, it caused leakage of the inner electrolyte. Using Sony's unique technology used in electronic device manufacturing, which is to do with surface process technology, Sony has managed in enhancing the accuracy of processing, succeeding to achieve anti-corrosion and to prevent liquid leakage at the same time.

Additionally, a Sony-unique active cathode material, which Sony has adopted from its current cells, has high hydrogen absorption capacity, resulting in the maintenance of a safe cell. (i.e. problem of cell expansion caused by hydrogen gas is solved). In addition, as a typical evaluation parameter of batteries, it has been achieved to improve the battery conservation capabilities as well.
As for the patents related to the development of mercury-free silver oxide batteries, applications of 5 patents have already been made in Japan, USA and Europe.

Sony will target to eliminate mercury from all Silver Oxide battery cells and will continue to pursue the advancement of environment-conscious technology.

Source: Sony Corp.

Explore further: ELaNa XIV CubeSats launch on JPSS-1 mission

Related Stories

ELaNa XIV CubeSats launch on JPSS-1 mission

November 20, 2017

NASA has launched four small research satellites, or CubeSats, developed by four universities as part of a broader mission launching the next generation polar-orbiting satellite to space. These CubeSat missions were selected ...

Synthetic material acts like an insect cloaking device

November 3, 2017

Synthetic microspheres with nanoscale holes can absorb light from all directions across a wide range of frequencies, making them a candidate for antireflective coatings, according to a team of Penn State engineers. The synthetic ...

Recommended for you

Physicists design $100 handheld muon detector

November 20, 2017

At any given moment, the Earth's atmosphere is showered with high-energy cosmic rays that have been blasted from supernovae and other astrophysical phenomena far beyond the Solar System. When cosmic rays collide with the ...

The strange case of the scuba-diving fly

November 20, 2017

More than a century ago, American writer Mark Twain observed a curious phenomenon at Mono Lake, just to the east of Yosemite National Park: enormous numbers of small flies would crawl underwater to forage and lay eggs, but ...

Recurring martian streaks: flowing sand, not water?

November 20, 2017

Dark features on Mars previously considered evidence for subsurface flowing of water are interpreted by new research as granular flows, where grains of sand and dust slip downhill to make dark streaks, rather than the ground ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.