Sheet-like Rechargeable Battery Developed Using New Principle

2014/02/24 16:04
Kouji Kariatsumari & Tsunenori Tomioka, Nikkei Technology Online
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Micronics Japan Co Ltd developed a technology to mass-produce the "battenice" rechargeable battery, which is based on a new principle, in collaboration with Guala Technology (a firm based in Kobe City, Japan).

The battenice is not categorized as a chemical cell but as a physical cell using quantum technology. They prototyped a sheet-like cell having a size of 100 x 100mm and a thickness of 11μm. When the cell is charged for about a minute with two AA cells connected in series, it can power a small fan for more than a minute.

In addition, the rotation speed of the fan hardly changes because, unlike an electric double-layer capacitor, the voltage of the cell does not lower proportionally as it discharges. In other words, its voltage is constant like that of a chemical cell.

According to Micronics Japan, it is possible to realize a cell that has a voltage of 1.5V, an energy density of 500Wh/L, an output density of 8,000W/L, a cycle life (the number of charge/discharge cycles that lowers the capacity of the cell to less than 90% of the initial capacity) of 100,000 cycles and an operating temperature range of -25 to +85°C.

For the prototype, Micronics Japan used a 10μm stainless-steel foil as a substrate and formed a "battery layer" on one side of the substrate. But the company aims to realize the above-mentioned specifications by using an aluminum foil, which is thinner and has a lower specific gravity, as a substrate and forming a battery layer on both sides.

In brief, the cell uses n-type metal-oxide semiconductor (e.g. titanium dioxide (TiO2), tin oxide (SnO2) and zinc oxide (ZnO)) particles covered with an insulating film (an insulating resin or inorganic insulator) for the charge layer.

A number of new energy levels are formed in the bandgap (gap between valence and conduction bands) of the n-type metal-oxide semiconductor by applying ultraviolet light to the charge layer under certain conditions in the manufacturing process. Electrons come into the levels at the time of charging the cell, and they are released at the time of discharging it. As a result, it functions as a rechargeable battery.

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