Test cells of this bio battery have achieved power output of 50 mW, currently the world's highest level for passive-type bio batteries. The output of these test cells is sufficient to power music play back on a memory-type Walkman.
In order to realize the world's highest power output, Sony developed a system of breaking down sugar to generate electricity that involves efficiently immobilizing enzymes and the mediator (electronic conduction materials) while retaining the activity of the enzymes at the anode. Sony also developed a new cathode structure which efficiently supplies oxygen to the electrode while ensuring that the appropriate water content is maintained. Optimizing the electrolyte for these two technologies has enabled these power output levels to be reached.
Sugar is a naturally occurring energy source produced by plants through photosynthesis. It is therefore regenerative, and can be found in most areas of the earth, underlining the potential for sugar-based bio batteries as an ecologically-friendly energy device of the future.
Sony is going to continue its development of immobilization systems, electrode composition and other technologies in order to further enhance power output and durability, with the aim of realizing practical applications for these bio batteries in the future.
The research results presented here have been accepted as an academic paper at the 234th American Chemical Society National Meeting & Exposition in Boston, MA USA, and were announced yesterday.
The bio battery mechanism:
The newly developed bio battery incorporates an anode consisting of sugar-digesting enzymes and mediator, and a cathode comprising oxygen-reducing enzymes and mediator, either side of a cellophane separator. The anode extracts electrons and hydrogen ions from the sugar(glucose) through enzymatic oxidation as follows:
The newly developed bio battery incorporates an anode consisting of sugar-digesting enzymes and mediator, and a cathode comprising oxygen-reducing enzymes and mediator, either side of a cellophane separator. The anode extracts electrons and hydrogen ions from the sugar(glucose) through enzymatic oxidation as follows:
Glucose -> Gluconolactone + 2 H+ + 2 e-
The hydrogen ion migrates to the cathode through the separator. Once at the cathode, the hydrogen ions and electrons absorb oxygen from the air to produce water:
(1/2) O2 + 2 H+ + 2 e- -> H2O
Through this process of electrochemical reaction, the electrons pass through the outer circuit to generate electricity. 
Source: physorg
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