Void-size-matched hierarchical 3D titania flowers in porous carbon as an electrode for high-density supercapacitive charge storage

Porous carbon has been a commercial choice as supercapacitor electrode; however, a large fraction of micrometer-sized voids limits the charge storability. Here, we show that porous carbon derived from an agricultural byproduct (palm kernel shell) with their voids filled by flower-shaped 3D nanostructure of TiO2(TiO2@AC) acts as a low-cost electrode material for high energy density lithium ion capacitors (LIC) and supercapacitors. The size of the TiO2 flowers here is ideally suited to fit in the voids (similar to 1 mu m); thereby, the TiO2@AC offers larger available surface area than its components, enhanced cyclic stability due to the larger particle volume and enhanced ion diffusion pathways due to the hierarchical structure. The LIC fabricated using the TiO2@AC electrode with a lithium plate as counter electrode showed impressively larger potential window (2.0-4.5 V vs. Li/Li+) than that fabricated using pure porous carbon (2.0-4.0 V vs. Li/Li+), a high specific energy (E-S) at high specific power (P-S) (E-S similar to 113 W h kg(-1) @ P-S similar to 3.3 kW kg(-1)). Symmetric supercapacitors fabricated using the TiO2@AC in a neutral aqueous electrolyte (1 M Na2SO4) showed three times higher energy density than that fabricated using pure porous carbon with similar power density. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Porous carbon derived from an agricultural byproduct filled with flower-shaped 3D nanostructure of TiO2 (TiO2@AC) has been shown to be a low-cost electrode material for high energy density lithium ion capacitors and supercapacitors. This material offers larger available surface area, enhanced cyclic stability, and improved ion diffusion pathways, leading to significantly higher performance in terms of potential window, specific energy, and power density compared to pure porous carbon electrodes.