Sony has developed an environmentally-friendly prototype battery that runs on sugars and that can generate enough electricity to power a music player and a pair of speakers, the Japanese company said.

The bio battery's casing is made of a vegetable-based plastic. It measures 3.9 cm (1.5 inch) along each edge and works by pouring sugar solution into the unit, where enzymes break it down to generate electricity.

Test cells had an output of 50 milliwatts, Sony said.

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"Sugar is a naturally occurring energy source produced by plants through photosynthesis," Sony said in a statement.

"It is therefore regenerative, and can be found in most areas of the earth, underlining the potential for sugar-based batteries as an ecologically-friendly energy device of the future."

The company said it aims to produce the batteries for commercial use, without specifying when.

Sony was hit last year by the recall of millions of laptop batteries over fears they could catch fire.