Screening and activating small-molecule Se in microporous S-decorated/N-doped carbon spheres for an enhanced rate performance

Breaking the Se_n into short chains and accelerating the phase transformation kinetics are of fundamental importance in achieving high-performance Se cathodes. However, challenges remain in the unraveled function of the microporosity and strategy to increase the affinity of the host material towards active Se_n species. Herein, S-decorated N-doped carbon spheres with a range of micropores are prepared to regulate different sized short-chain Se_n. Combined with the density functional theory (DFT) simulation on the geometry of Se_n (2 ≤ n ≤ 8) small molecules, different micropores of the host in screening Se_n (2 ≤ n ≤ 8) with higher activity, accelerated kinetics and optimized performance are elaborated. The sulfur molecules decoration provides abundant polar sites to enhance the chemisorption of both Se_n and Li₂Se and thus boosting the redox kinetics and Se_n utilization rate of the Li-Se battery. The obtained S@NPC/Se-7 cathode displays an extraordinary rate capability (430.4 mAh g⁻¹ at 5 C) and maintains an ultrastable cycling property (at 1 C over 500 cycles).