Covalent Selenium Embedded in Hierarchical Carbon Nanofibers for Ultra-High Areal Capacity Li-Se Batteries.

Lithium selenium (Li-Se) batteries have attracted increasing interest for its high theoretical volumetric capacities up to 3,253 Ah L. However, current studies are largely limited to electrodes with rather low mass loading and low areal capacity, resulting in low volumetric performance. Herein, we report a design of covalent selenium embedded in hierarchical nitrogen-doped carbon nanofibers (CSe@HNCNFs) for ultra-high areal capacity Li-Se batteries. The CSe@HNCNFs provide excellent ion and electron transport performance, whereas effectively retard polyselenides diffusion during cycling. We show that the Li-Se battery with mass loading of 1.87 mg cm displays a specific capacity of 762 mAh g after 2,500 cycles, with almost no capacity fading. Furthermore, by increasing the mass loading to 37.31 mg cm, ultra-high areal capacities of 7.30 mAh cm is achieved, which greatly exceeds those reported previously for Li-Se batteries.