Highly intrinsically stretchable microsupercapacitor achieved by a post-growth-engineered electrode and zwitterionic ionogel electrolyte

The growing demand for compact and portable energy storage solutions for wearable devices has led to the development of conformal and deformable high-performance microsupercapacitors (MSCs). However, traditional MSCs face challenges in achieving high deformability without compromising performance. Herein, we present a soft electrode system comprising multiwalled carbon nanotubes/manganese phosphate nanoneedles/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate within an Ecoflex matrix. This system is prepared via phosphoric acid treatment, which forms nanoneedles with high aspect ratios, resulting in an enhanced surface area and porosity. Additionally, an ionogel containing a zwitterionic moiety is employed as an MSC electrolyte to ensure high conductivity and strong interfacial bonding. The fabricated MSC exhibits exceptional performance, with a specific capacitance of 304.2 mF cm⁻², energy density of 82.8 µWh cm⁻², and power density of 699.7 µW cm⁻². The capacitance retention exceeds 95%, even at 300% stretching, which is attributed to the intrinsic stretchability of the MSC. Furthermore, the present MSC device demonstrates outstanding reproducibility and stability, retaining 95.7% of its initial capacitance after 10,000 charge-discharge cycles and 97.8% after being stored for 21 days. This MSC can be interfaced with a microcontroller unit to facilitate wireless charging and discharging via a smartphone, thereby enabling the remote operation of healthcare devices.