Boosting ion dynamics through superwettable leaf-like film based on porous g-C3N4 nanosheets for ionogel supercapacitors

Abstract

Ionic liquid (IL) electrolytes have enormous potential for the development of high energy density supercapacitors (SCs) owing to their wide potential windows, but ILs are plagued by sluggish ionic diffusion due to their high viscosity and large ion size. Exploiting superwettable electrodes possessing high compatibility with IL electrolytes remains challenging. Inspired by the biological characteristics observed in nature, a unique film electrode with a Monstera leaf-like nanostructure is synthesized and used to overcome the aforementioned bottleneck. Similar to the pores in Monstera leaves that allow the permeation of air and water vapor, the film electrode is based on porous g-C₃N₄ nanosheets (~1 nm thick) as ion-accessible “highway” channels, allowing ultrafast diffusion of IL ions. The film exhibits a high diffusion coefficient (3.68 × 10⁻¹⁰ m² s⁻¹), low activation energy (0.078 mJ mol⁻¹) and extraordinary wettability in the IL electrolyte, indicating its superior IL ion dynamics. As a proof of concept, flexible ionogel SCs (FISCs) with tailorability and editability are fabricated, which exhibit a high energy density (10.5 mWh cm⁻³), high-power density, remarkable rate capability, and long-term durability, outperforming previously reported FISCs. Importantly, these FISCs can be effectively charged by harvesting sustainable power sources, particularly the rarely studied wind power, for practical applications.

Supercapacitors: leaf-like materials make energy harvesting a breeze

Battery alternatives known as supercapacitors can be fabricated into bendable devices that tap into wind power. Researchers looking to pack more energy into supercapacitors are replacing conventional electrolytes with ionic liquids made from viscous organic salts. Minjie Shi at the Jiangsu University of Science and Technology in Zhenjiang, China, and colleagues have designed a supercapacitor electrode that accelerates the sluggish movements of ionic liquids by mimicking channels used by leaves to transport air and water vapor. The team’s electrode contains tiny pathways for ionic liquids to move, thanks to a structure of porous carbon nitride nanosheets held together by carbon nanotube composites. Supercapacitors made with the new electrode had improved performance compared to other ionic liquid-based devices, and could be used for energy-harvesting applications including bicycle-mounted recharging using miniature wind turbines.