Flexible energy storage devices based on nanomaterials

Flexible electronics in mobile environments such as those encountered in wearable devices also require energy sources. Ideally the energy source, typically batteries and supercapacitors, should also be flexible and have the same form factor as the electronic system. This has given rise to a new paradigm of flexible energy storage devices. The requirement for flexibility imposes limits on thickness of the component parts of a battery or supercapacitor. As a result the current collectors, electrode layers and the electrolytes all have to be thin enough and not crack or disintegrate under repeated cycles of flexing to the specified minimum arc diameter, typically 1 - 5 cm. In order to achieve sufficient reaction surface/volume in thin film form to have the required energy/power capacity nanomaterial formulations of the electrode become essential. The electrolyte requirements for a flexible energy storage device are particularly challenging. Hermetic sealing of a liquid electrolyte in a flexible package is never ideal. This leads to loss of electrolyte and performance over unacceptable short times. Solid electrolytes are therefore preferred, but they have higher resistance than their liquid counterparts and lead to a loss in performance. Recent developments in flexible batteries. Flexible primary and secondary batteries based on aqueous electrolytes being researched by the authors are introduced. Nanomaterial enhanced solid electrolytes for flexible Zn-MnO2 batteries are also introduced.