In Situ Encapsulation of Cobalt Selenide Nanoparticles in N-Doped Carbon Nanotubes with a Full Sulfiphilic Surface as a Catalytic Interlayer for Lithium–Sulfur Batteries

Abstract

The shuttle effect of lithium−sulfur batteries (LSBs) caused by the dissolution and migration of lithium polysulfides (LiPSs) leads to rapid capacity decay of sulfur cathodes. Modifying the separator with a catalytic layer becomes an effective strategy to inhibit LiPS shuttling and promote the conversion kinetics of sulfur active materials. Herein, we propose a carbon nanotube (CNT)-encapsulation strategy to fabricate a composite of CoSe nanoparticles encapsulated in N-doped CNT (CoSe@NCNT). The as-prepared CoSe@NCNT is endowed with a full sulfiphilic surface to trap LiPSs by Co−S and Se−Li bonds and catalyze sulfur redox reactions (SRRs) of the discharge/charge processes. In addition, the encapsulated structure effectively inhibits the aggregation of CoSe nanoparticles and enables its persistent adsorption−catalysis ability on regulating the kinetics of SRRs. When equipped with a CoSe@NCNT catalytic interlayer, the LSB shows a high specific capacity of 768.3 mAh g −1 at 2 C and superior cycle stability with the capacity decay rate of 0.06% per cycle over 1000 cycles at 1 C. In addition, when operated with an electrolyte/sulfur ratio of 5 μL mg −1 , the modified battery with a sulfur loading of 4.0 mg cm −2 delivers a specific capacity of 746.9 mAh g −1 at 0.2 C. Our studies provide a CNT-encapsulation strategy to develop transition metal-based catalytic materials for high-performance LSBs.

Multifunction of MXene in Lithium–Sulfur Batteries: A Review

“…Lithium–sulfur batteries (LSBs) are a novel kind of energy storage system with a sulfur cathode and metal lithium anode. It has a high theoretical specific capacity and theoretical energy density, which is 1675 mAh g –1 and 2600 Wh kg –1 . − However, it also faces serious problems in practical applications: − (i) The electron-insulating nature of S and Li 2 S impedes redox reactions, leading to low utilization of S. (ii) The shuttle effect of soluble lithium polysulfide Li 2 S n (4 ≤ n ≤ 8) that emerged during the charge/discharge process will cause the wastage of active substances. (iii) The density variations between S and Li 2 S makes the cathode produce 80% volume expansion after complete discharge, resulting in electrode damage.…”