Nitrogen-doped nanotubes and few-layer montmorillonite composites as an effective polysulfides adsorbent for lithium–sulfur batteries

Abstract

With the advantages of high specific energy and high theoretical capacity, lithium‑sulfur batteries are gaining attention in the field of energy storage. However, there are still many difficulties in the practical application. Such as poor electrical conductivity of sulfur, large volume expansion of sulfur, shuttle effect of polysulfide, resulting in rapid capacity decay and poor cycling stability. To solve these problems, in this paper, nitrogen-doped carbon nanotube and layer less montmorillonite composites (NMMT/CNT/S) were prepared by a simple hydrothermal method and used as sulfur carriers for lithium‑sulfur batteries. Due to the high conductivity of carbon nanotubes, the high specific surface area and large number of adsorption sites in montmorillonite, and the ability of nitrogen to increase electrochemical reactivity, the obtained NMMT/CNT/S has excellent electrochemical performance: Initial discharge capacity up to 1122 mAh/g at a current density of 0.5C, initial specific capacity of 1017 mAh/g at a current density of 1C, capacity remaining after 100 cycles 815 mAh/g, the capacity retention rate is 80.1 %. The prepared NMMT/CNT/S cathode material has good magnification performance, at current densities of 0.2, 0.5, 1, 2 and 4C, the average specific capacity was 1085.9, 902.2, 820.4, 681.2 and 526.4 mAh/g, respectively. The initial specific capacity of NMMT/CNT/S at a current density of 2C is 698 mAh/g, capacity remaining 542 mAh/g after 500 cycles of stabilization, with a capacity retention rate of 77.7 %. These results show that the prepared NMMT/CNT/S is a breakthrough development in the application of lithium‑sulfur batteries.