Manganese phosphate nanoneedle-nanoflower hybrid electrodes with strain-tolerant carbon nanotube percolation networks for stretchable microsupercapacitors

Stretchable energy storage devices face a trade-off between mechanical deformability and electrochemical performance. Here, we report a stretchable microsupercapacitor based on a hybrid electrode of manganese phosphate nanoneedles (MPNNs) and nanoflowers (MPNFs) with carbon nanotubes and acid-treated PEDOT in an Ecoflex matrix. The high-aspect-ratio 1D nanoneedles confine CNTs through an excluded-volume effect, holding the percolation network in a compact arrangement that suppresses resistance increase under strain. The 3D nanoflowers provide the surface area required for charge storage. Coupled with a zwitterionic ionogel electrolyte, the optimized device delivers an areal capacitance of 229.4 mF cm⁻², an energy density of 62.5 μWh cm⁻², and a power density of 347.2 μW cm⁻². The device retains 96.6% capacitance at 300% tensile strain and sustains stable charge-discharge behavior over 10,000 stretch-release cycles to 300% strain. On-body operation of solar-charged LED displays and a GPS tracker confirms device performance under practical wearable conditions.