High Selenium Loading in Vertically Aligned Porous Carbon Framework with Visualized Fast Kinetics for Enhanced Lithium/Sodium Storage

Lithium/sodium-selenium (Li/Na-Se) batteries with high volumetric specific capacity are considered promising as next-generation battery technologies. However, their practical application is hindered by challenges such as low Se loading in cathodes and the polyselenides shuttle effect. To address these challenges, a new Se host is introduced in the form of a free-standing N, O co-doped vertically aligned porous carbon framework decorated with a carbon nanotube forest (VCF-CNTs), allowing for high mass loading of up to 16 mg cm-2. The low-tortuosity Se@VCF-CNTs architecture facilitates rapid lithiation/sodiation kinetics, while the CNT forests in vertical microchannels enhance efficient Se loading and serve as a multi-layer fence to prevent undesired polyselenide shuttling. Consequently, the Se@VCF-CNTs cathode displays a significant areal capacity of 10.3 mAh cm-2 at 0.1 C with a Se loading of 16 mg cm-2 for Li-Se batteries, exceeding that of commercial lithium ion batteries (4.0 mAh cm-2). In Na-Se batteries, the Se@VCF-CNTs electrode with a Se loading of 5 mg cm-2 exhibits a discharge capacity of 436 mAh g-1 after 200 cycles, proving its consistent cycling performance. This study enriches the field of knowledge concerning high-loading Se-based battery systems, offering a promising avenue for enhancing energy density in the field. Free-standing N, O co-doped vertical aligned porous carbon framework adorned with a carbon nanotube forest (VCF-CNTs) is introduced as the host for Lithium/sodium-selenium batteries, enabling high selenium (Se) loading, which can improve the energy density. The lithiation/sodiation mechanism of the Se@VCF-CNTs is investigated by combining in situ synchrotron X-ray diffraction, in situ transmission electron microscope, and electroanalytical technique. image