Highly Stretchable Alkaline Batteries Based on an Embedded Conductive Fabric

Abstract

Recent progress in the fabrication of ultrathin silicon ribbons and novel architectures have enabled devices that can stretch, bend, and twist without mechanical fatigue or changes in operational performance. [ 1–5 ] These advances have lead to compliant, conformable electronics for health monitoring and sensing purposes. [ 6 , 7 ] For true autonomous operations, these devices require an equally accommodating power source. Existing commercially available power sources are too bulky and negate the advantages of these compliant/fl exible devices. We demonstrate a stretchable battery with electrochemically active materials embedded in a compliant conductive fabric, which acts as a support for the material. The assembled manganese dioxide (MnO 2 ) zinc (Zn) stretchable cell with a polyacrylic acid (PAA) based polymer gel electrolyte (PGE) had an open circuit potential (OCV) of 1.5 V and a capacity of 3.875 mAh/cm 2 . The capacity remained constant when tested under strain as high as 100%. Two cells connected in series continuously powered an LED when stretched to 150% and twisted by 90 degrees. In the past decade, stretchable electronics with a wide variety of functionality such as biological sensors, [ 8 ] solar cells, [ 9 ] polymer light-emitting devices, [ 10 ] transistors, [ 11 , 12 ] active matrix displays, [ 13 , 14 ] and photo-detectors [ 15 ] have been demonstrated. While there has been progress on power sources with similar mechanical properties, there is still a signifi cant gap. Previously, stretchable supercapacitors based on SWNT deposited on stretched PDMS, [ 16 ] CNTs embedded in fabric [ 17 ] and conducting polymer on compliant substrates [ 18 ] have been demonstrated, but these devices are suited to short term energy storage and cannot be used to power standalone devices. A stretchable MnO 2 -Zn primary battery with a stretchable carbon oil current collector was demonstrated, however the discharge capacity decreased by ∼ 55% when the battery was stretched by 50%. The discharge profi le showed a high ohmic potential drop (I × R) at the start of discharge for the strained battery. Drop in potential can be accounted by decrease in electrical conductivity of the carbon oil current collector and loss in electrical contact in the electrode when stretched. [ 19 ]