3D hierarchical networks constructed from interlayer-expanded MoS2 nanotubes and rGO as high-rate and ultra-stable anodes for lithium/sodium-ion batteries

Abstract

Unsatisfactory cycling stability and rate capability due to volume expansion and poor electrical conductivity greatly hinder the practical application of MoS₂-based materials. Aiming to address these issues, a novel 3D hierarchical conductive network architecture consisting of MoS₂ nanotubes derived from self-assembled ultrathin MoS₂ nanosheets with in situ N-doped carbon intercalation and reduced graphene oxide used as an encapsulating function (NC-MoS₂@rGO) were effectively achieved. Due to many advantages mainly including hollow tubes, ultrathin MoS₂ nanosheets, expanded interlayer spacing and highly conductive rGO wrapping, this architecture achieves more active sites, faster electron and ion transport rates, and greater structural stability. These advantages are finally attributable to the excellent electrochemical performance of lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs). In LIBs, NC-MoS₂@rGO displays a high specific capacity of 1308.6 mA h g⁻¹ at 0.2 A g⁻¹ after 200 cycles, superior rate capability (834.2 mA h g⁻¹ at 10 A g⁻¹), and ultra-long cycle stability (528.4 mA h g⁻¹ at 5 A g⁻¹ after 6590 cycles). In addition, the electrode also obtained the expected discharge capacity (554.8 mA h g⁻¹ at 0.2 A g⁻¹ after 200 cycles) and cycle stability (463.6 mA h g⁻¹ at 1 A g⁻¹ after 1000 cycles and 383.2 mA h g⁻¹ at 2 A g⁻¹ after 1500 cycles) in Na ion storage. Furthermore, we elucidated the highly reversible electrochemical storage behavior of Na ions by using the ex situ X-ray diffraction (XRD) technique. Density functional theory (DFT) calculations further prove the positive effect of the added graphene on the improvement of battery performance.