A High-Performance Micro Lithium-Ion Capacitor with 3D Interdigital Electrodes for On-Chip Energy Storage

We present an advanced on-chip lithium-ion microcapacitor with the 3D interdigital activated carbon cathode and the novel-designed TiO2-based anode for the first time. The well-dispersed TiO2 nanoparticles provide fast pathways for ion diffusion and a large surface area for the reaction, enhancing the power density. The TiO2 nanoparticles are distributed in the cross-linked network of Ti3C2 (one of 2D transition metal carbides) and disordered carbon (DC), which provide conductive channels to improve electrode dynamics and enhance cyclability. The one-step oxidation by hydrothermal method neither needs a relatively high temperature nor extra titanium source. Moreover, the micro 3D interdigital electrodes maintain a short transmission distance of ions between electrodes to achieve the ultrahigh power density and enlarge the capacitance by increasing the amount of material with the heightened electrodes. It exhibits a superior capacitance of 12.7 mF cm⁻² and excellent cycling stability of 70% retention after 200 cycles. Furthermore, the device prepared by microfabrication technology could be compatible and integrated with the on-chip applications in MEMS devices and portable electronics, showing great advantages compared with traditional electrolytic capacitors.