Bending Properties of Solid Thin Flexible Energy Storage Devices

The performance of solid, thin and flexible electrochemical capacitors (ECs) under different bending conditions were investigated. The bending parameters include bending angle, bending radius and bending cycle. While the bending angle does not affect the performance of the solid EC cells significantly, small bending radius increases the cell resistance from a delamination at the current collector/electrode interface. A large bending cycle causes a severe self-discharging by losing mechanical protection at the electrolyte/separator layer. The layer is pierced through, creating localized contacts between electrodes which lead to a high leakage current. The electrode/electrolyte interface remains relatively intact under various bending conditions. The investigation of these parameters together with cross-sectional analyses provide a systematic understanding of the failure mechanism of thin and flexible ECs under bending. Although the approach was demonstrated on a sandwiched solid EC cell with a commercial activated carbon and a neutral pH polymer electrolyte, it can be extended for quantified investigations of mechanical properties of general solid flexible electrochemical devices.