A 4 V Planar Li-ion Micro-Supercapacitor with Ultrahigh Energy Density

Hybrid ion microsupercapacitors, expected to acquire considerable energy density without sacrificing their power density, still remain challenges due to the lack of appropriate assembly processes and reasonable kinetics matching. Herein, an in-plane Li-ion microsupercapacitor (LIMC) consisting of in situ prelithiated faradaic anode and highly porous nonfaradaic cathode was developed by a laser-assisted method. Benefiting from a fast ion adsorption/desorption process on the cathode and surface-controlled multielectron redox reaction on the anode, the LIMC exhibits a wide working window of 4 V and high areal capacitance of 135.4 mF/cm² (150.4 μAh/cm²) at 0.1 mA/cm². The energy density reaches 301 μWh/cm² (256 mWh/cm³), higher than most state-of-the-art metal ion microsupercapacitors reported previously. A single device could drive an electronic watch (∼1.5 μW) for more than 2 h after charging for 15 min. The high engineering compatibility and integrity of materials and electrodes demonstrated in this work provide a reference for future microelectronics with high energy output.