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.