Tuning the micropore/mesopore ratio of chitin-derived hierarchically porous carbon for high-performance lithium-selenium batteries.

Lithium-selenium (Li-Se) batteries are considered a promising energy storage alternative, mainly because of the high theoretical volumetric capacity of selenium cathodes. However, the polyselenide shuttle effect, large volume expansion and slow diffusion kinetics during cycling continue to impede their practical application. Herein, we report an enhancement of the Li+ diffusion kinetics via tuning the micropore/mesopore ratio of the chitin-derived hierarchically porous carbon for Li-Se batteries. In this structure, confining Se in the hierarchically porous carbon matrix leads to the direct formation of Li2Se through a solid-solid reaction. The incorporation of the tailored proportion of mesopores provides fast pathways for ion diffusion. This enables rapid electric double layer formation in the micropores, leading to improved rate performance and specific capacity. In addition, the hierarchically porous carbon provides buffer space to mitigate cathode volume changes during cycling. Consequently, the constructed Se@ZnCl2-BPC cathode shows exceptional cycling stability, with an initial capacity of 303.1 mA h g-1 at 2C and a capacity retention of 90.6% after 1000 cycles. As far as we know, this is the first report of engineering porosity for Li-Se batteries. It is believed that our work could underscore the critical importance of the pore ratio of hierarchically porous carbon engineering for developing high-performance Li-Se batteries.