Boosting Ion Diffusion Kinetics of MXene Inks with Water‐in‐Salt Electrolyte for Screen‐Printed Micro‐Supercapacitors

Abstract

Flexible wearable electronics are in urgent need of advanced micro‐energy storage devices. MXenes are widely used in supercapacitors because of their excellent conductivity and hydrophilicity. Nevertheless, MXene‐based supercapacitors typically exhibit low capacitance and unsatisfied rate performance, particularly in the solid compact MXene film electrode with limited porosity and/or ion diffusion paths. Here, the synthesis of MXene inks with enlarged interlayer spacing for facilitated ion diffusion kinetics by intercalating lithium ions is reported. The ion‐intercalated MXene inks are further screen‐printed for scalable production of MXene‐based micro‐supercapacitors (MSCs). Benefiting from such an electrode architecture design, as well as the wide voltage window of 21 m bis(trifluoromethane)sulfonimide lithium (LiTFSI) water‐in‐salt electrolyte, the device exhibits impressive areal capacitance (252 mF cm−2), much‐improved rate performance (capacitance retention rate as high as 80%), excellent cyclic stability (retains 98.4% of initial capacitance after 10 000 cycles) and flexibility, showing great potential in the field of wearable intelligent electronics.

Sulfur-Functionalized Carbon Nanotubes with Inlaid Nanographene for 3D-Printing Micro-Supercapacitors and a Flexible Self-Powered Sensing System

“…The iterative advancement of microscale electronic systems necessitates the development of portable, miniaturized energy storage devices with superior electrochemical performance, exceptional customization, and excellent mechanical flexibility. − Micro-supercapacitors (MSCs) have garnered significant attention as a promising solution for miniaturized energy storage due to their unparalleled high-power density, robust mechanical properties, and long cyclic stability. − Recently, carbonaceous nanomaterials have emerged as the promising electrode candidates for microscale MSCs. , One-dimensional (1D) carbon nanotubes (CNTs), for instance, exhibit high aspect ratios, outstanding physicochemical properties, and excellent flexibility, alongside additional benefits such as mechanical robustness, lightweight nature, and ease of handling. − Moreover, assembling 1D CNTs into three-dimensional (3D) interconnected networks is conductive to efficient electron transportation and ionic storage, significantly enhancing capacitance performance in confined spaces . The 3D-printing technique, particularly direct ink writing (DIW), has emerged as a cutting-edge additive manufacturing method for fabricating 3D-structured electrodes. − This technique effectively caters to the specific design, integration, and functional requirements of CNTs-based MSCs. Notably, the development of suitable CNTs-based ink with optimized rheological behaviors and enhanced electrochemical properties is crucial for achieving high-performance MSCs. , …”