Scientists have developed a flexible nitroxide polymer coating that can be used as an electrode in organic rechargeable batteries. This could enable a printing process for batteries in small, bendable electronic devices such as smart cards and wearable sensors. 

As technology advances and electronic devices get more compact, there is a growing need for versatile battery power options. Recently organic polymers bearing radical side groups have been successfully used to develop flexible polymer films as batteries. Now Hioyuki Nishide and coworkers at the Waseda University in Tokyo have developed a nitroxide polymer coating that can be cured directly onto any shaped surface without the need for tedious purification processes. The polymer exhibits rapid and almost stoichiometric redox activity. 

'We have been studying such flexible batteries for years,' says Nishide, 'however, it has not been easy to prepare the polymer electrode with good adhesion on a current collector. This simple curing process under mild, open-air conditions could enable wet-fabrication processes such as printing.' 

Nishide used click-type Michael polyadditions to form a crosslinked polymer network bearing nitroxide radicals without any unwanted side reactions. The step-growth Michael additions formed a geometrically homogenous 3D network with desirable mechanical properties and high adhesion to any type of current collector. The dense population of nitroxide radicals allows rapid, high capacity, reversible storage. 

Samy Elangovan, an expert in energy related materials at the North Dakota State University, Fargo, US says, 'organic-based electrodes display advantages over inorganic-based (lithium-ion) batteries, because of their flexibility, tunable electrical properties, and their non-hazardous disposal. Given the vast room available for further tuning, these organic-based batteries can soon see commercial application in flexible electronics.' 

Jacob Bush 

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