Super‐Stretchable and High‐Energy Micro‐Pseudocapacitors Based on MXene Embedded Ag Nanoparticles

Abstract The advancement of aqueous micro‐supercapacitors offers an enticing prospect for a broad spectrum of applications, spanning from wearable electronics to micro‐robotics and sensors. Unfortunately, conventional micro‐supercapacitors are characterized by low capacity and slopy voltage profiles, limiting their energy density capabilities. To enhance the performance of these devices, the use of 2D MXene‐based compounds has recently been proposed. Apart from their capacitive contributions, these structures can be loaded with redox‐active nanowires which increase their energy density and stabilize their operation voltage. However, introducing rigid nanowires into MXene films typically leads to a significant decline in their mechanical properties, particularly in terms of flexibility. To overcome this issue, super stretchable micro‐pseudocapacitor electrodes composed of MXene nanosheets and in situ reconstructed Ag nanoparticles (Ag‐NP‐MXene) are herein demonstrated, delivering high energy density, stable operation voltage of ≈1 V, and fast charging capabilities. Careful experimental analysis and theoretical simulations of the charging mechanism of the Ag‐NP‐MXene electrodes reveal a dual nature charge storage mechanism involving ad(de)sorption of ions and conversion reaction of Ag nanoparticles. The superior mechanical properties of synthesized films obtained through in situ construction of Ag‐NP‐MXene structure show an ultra stretchability, allowing the devices to provide stable voltage and energy output even at 100% elongation.