Solvent exchange assisted 3D printing of low tortuosity thick electrode for high areal energy density and power density supercapacitors

The pursuit of higher energy density for supercapacitors holds enormous practical significance but remains an arduous task. Three-dimensional (3D) thick electrode has emerged as a promising approach for optimizing the utilization of Z-axis space to enhance the energy density of supercapacitors, yet suffering from the limitations of poor mechanical stability and sluggish electron/ion transport. Herein, a solvent exchange assisted 3D printing technique is proposed in this work that allows for the construction of high mass loading, low tortuosity, and high energy and power density supercapacitors. The electrode is composed of carbon nanotubes and cellulose triacetate that are intertwined to create a 3D network uniformly enveloping around the active carbon. This ensures rapid electron transfer and stress release throughout the electrode. Furthermore, the solvent exchange process induces low tortuosity aligned micro-channels, which act as high-speed paths for ion diffusion, overcoming the limitation of sluggish ion transport in 3D thick electrode as the mass loading increases. As a result, the assembled symmetric supercapacitor delivers a superior rate performance (61.3 %, 1–100 mA cm−2) and cycling stability (94 % after 25000 cycles), and presents an impressive areal energy/power density (0.72 mWh∙cm−2/174.4 mW cm−2), outperforming most reported carbon-based electrochemical double-layer capacitors (EDLC) supercapacitors. This work offers an exciting prospect for the fabrication of high-performance energy storage devices with exceptional areal and power energy density, addressing the challenges faced in an energy-fraught era.