NEC Develops New Ultra-Thin, Flexible, Rechargeable Battery

Tokyo – NEC has succeeded in the development of an ultra-thin, flexible, rechargeable battery capable of super-fast (30-second) charging, which can be embedded into smartcards and intelligent paper. The new battery, organic radical battery (ORB), uses a type of plastic called organic radical polymer as its cathode.

Organic radical polymer assumes an electrolyte-permeated gel state, and is the reason why the rechargeable battery is so remarkably flexible and pliant. In addition, the organic radical polymer electrode reaction is extremely fast and the supporting salts migrate through gel state polymer very smoothly. This results in little resistance to the charging reaction and an incredibly fast charging time of less than 30 seconds. Not only is this new battery thin, flexible and rechargeable, but it is also environmentally friendly as unlike conventional rechargeable batteries, it does not contain any harmful heavy metals such as mercury, lead or cadmium.

Key features of the newly developed battery include:

• An exceedingly thin structure (300 microns), which will enable it to be embedded into objects such as smartcards and intelligent paper in the future.
• A pliant and bendable structure, as flexible plastic is used as the cathode material.
• An ultra-fast charging speed of less than 30 seconds.
• A high energy density of approximately 1 mWh (mili Watt hour) per cm squared. This means, for example, that if the ORB was used in an active RFID device, it would support up to approximately several tens of thousands of signal transmissions on a single charge.
• Environmentally friendly, it does not contain any harmful metals.

NEC anticipates that its new and unique battery will be used extensively in the future to power all kinds of tiny ubiquitous terminals. The interconnection of networks with battery-powered next generation ubiquitous devices will enable all kinds of objects to become terminals, bringing us closer to a ubiquitous networked society by allowing access to the network anytime, anywhere.

Glossary

Organic radical battery
NEC first proposed the use of an organic radical compound as a battery's electrode active material in 2000. Charging occurs through the oxidation-reduction (redox) reaction of the radical region. The ORB exhibits an extraordinarily high discharge rate (large current discharged at one time). NEC was commissioned by the New Energy and Industrial Technology Development Organization (NEDO) during the period November 2002 to March 2005 to develop a battery for data backup on desktop PCs, which fully exploits the advantageous characteristics of ORBs.

Organic radical polymer
Polymer (a type of plastic) that has a stable radical in the molecular structure. While generally unstable, the radical in this case is made stable by the unique molecular structure.

Electrolyte-permeated gel state
This is the state in which polymer suffused with solvent expands. It is an intermediate material state between solid and liquid.