Y.Y. Zhu†, Q.X. Zhang†, J.X. Ma, P. Das, L.Z. Zhang, H.Q Liu, S. Wang, H. Li*, Z.-S. Wu*

Carbon Energy, 2024, e481.

DOI: 10.1002/cey2.481 [PDF]

The fast-growing miniaturization, integration, and intelligence of electronic devices, have pushed the demand for customizable micro-supercapacitors (MSCs) outputting high energy density. However, efficient microfabrication of safe and high energy MXene MSCs for integrating microelectronics remains a grand challenge due to low voltage window in aqueous electrolytes (typically ≤ 0.6 V) and limited areal mass loading of MXene microelectrodes. Here we address these challenges by developing a high-concentration (18 mol kg1) “water-in-LiBr” (WiB) gel electrolyte for MXene symmetric MSCs (M-SMSCs) demonstrating a record high voltage window of 1.8 V. Subsequently, additive-free aqueous MXene ink with excellent rheological behavior was developed for 3D printing customizable all-MXene microelectrodes on various substrates. Leveraging the synergy of high-voltage WiB gel electrolyte and 3D-printed microelectrodes, quasi-solid-state M-SMSCs stably working at 1.8 V were constructed, and achieved an ultrahigh areal energy density of 1753 μWh cm−2 and long-term operation at 40 °C, with excellent low-temperature resistance properties. Finally, by extending the 3D printing protocol, M-SMSCs were integrated with humidity sensors on a single planar substrate, demonstrating its reliability in miniaturized integrated microsystems.