SnS2 monolayer and SnS2/graphene heterostructure as promising anchoring materials for lithium-sulfur batteries: A computational study

Construction of SnS2-modified multi-hole carbon nanofibers with sulfur encapsulated as free-standing cathode electrode for lithium sulfur battery

Lithium-sulfur (Li-S) batteries exhibit a huge potential in energy storage devices for the thrilling theoretical energy density (2600 Wh kg-1). Nevertheless, the serious shuttle effect rooted in polysulfides and retardative hysteresis reaction kinetics results in inferior cycling and rate performances of Li-S batteries, impeding commercial applications. In order to further promote the energy storage abilities of Li-S batteries, a unique binder-free sulfur carrier consisting of SnS2-modified multi-hole carbon nanofibers (SnS2-MHCNFs) has been constructed, where MHCNFs can offer abundant space to accommodate high-level sulfur and SnS2can promote the adsorption and catalyst capability of polysulfides, synergistically promoting the lithium-ion storage performances of Li-S batteries. After sulfur loading (SnS2-MHCNFs@S), the material was directly applied as a cathode electrode of the Li-S battery. The SnS2-MHCNFs@S electrode maintained a good discharge capacity of 921 mAh g-1after 150 cycles when the current density was 0.1 C (1 C = 1675 mA g-1), outdistancing the MHCNFs@S (629 mAh g-1) and CNFs@S (249 mAh g-1) electrodes. Meanwhile, the SnS2-MHCNFs@S electrode still exhibited a discharge capacity of 444 mAh g-1at 2 C. The good performance of SnS2-MHCNFs@S electrode indicates that combining multihole structure designation and polar material modification are highly effective methods to boost the performances of Li-S batteries.

Cobalt-doped tin disulfide catalysts for high-capacity lithium-air batteries with high lifetime

Dual electrolyte lithium-air batteries have received widespread attention for their ultra-high energy density. However, the low internal redox efficiency of these batteries results in a relatively short operating life. SnS2 is widely used in Li-S batteries, Li-ion batteries, photocatalysis, and other fields due to the high discharge capacity in batteries. However, SnS2 suffers from low electrical conductivity and slow redox kinetics. In this study, Co-doped SnS2 is prepared by hydrothermal method for application in dual-electrolyte lithium-air batteries to study its electrochemical performance and its catalytic reaction process by DFT theory. Conductivity tests show that the Co doping enhances the electrical conductivity of the material and high transmission electron microscopy (HRTEM) results demonstrate that the Co doping of SnS2 increases the grain plane spacing and the material indicates that defects are created on the surface of the material, which is more beneficial to the electrochemical performance of the cell. Co-doped SnS2 exhibits excellent good cycling stability and high discharge capacity in a dual electrolyte lithium-air battery, maintaining a 0.7 V overpotential for 120 h at a current density of 0.1 mA cm-2, with a cell life of over 500 h and an initial discharge capacity showing excellent results up to 16 065 mA h g-1. In addition, this study explores the catalytic activity of Co-doped SnS2 based on density flooding theory (DFT). The results show that Co atoms have a synergistic effect with Sn atoms to perturb the lattice parameters. The calculations show that the catalytic activity is enhanced with the increasing of Co doping content and 3Co-Sn exhibits minimal overpotential.

Synergistically Accelerating Adsorption-Electrocataysis of Sulfur Species via Interfacial Built-In Electric Field of SnS2 -MXene Mott-Schottky Heterojunction in Li-S Batteries

Developing efficient heterojunction electrocatalysts and uncovering their atomic-level interfacial mechanism in promoting sulfur-species adsorption-electrocatalysis are interesting yet challenging in lithium-sulfur batteries (LSBs). Here, multifunctional SnS₂ -MXene Mott-Schottky heterojunctions with interfacial built-in electric field (BIEF) are developed, as a model to decipher their BIEF effect for accelerating synergistic adsorption-electrocatalysis of bidirectional sulfur conversion. Theoretical and experimental analysis confirm that because Ti atoms in MXene easily lost electrons, whereas S atoms in SnS₂ easily gain electrons, and under Mott-Schottky influence, SnS₂ -MXene heterojunction forms the spontaneous BIEF, leading to the electronic flow from MXene to SnS₂ , so SnS₂ surface easily bonds with more lithium polysulfides. Moreover, the hetero-interface quickly propels abundant Li⁺ /electron transfer, so greatly lowering Li₂ S nucleation/decomposition barrier, promoting bidirectional sulfur conversion. Therefore, S/SnS₂ -MXene cathode displays a high reversible capacity (1,188.5 mAh g^-1 at 0.2 C) and a stable long-life span with 500 cycles (≈82.7% retention at 1.0 C). Importantly, the thick sulfur cathode (sulfur loading: 8.0 mg cm^-2 ) presents a large areal capacity of 7.35 mAh cm^-2 at lean electrolyte of 5.0 µL mg_s ^-1 . This work verifies the substantive mechanism that how BIEF optimizes the catalytic performance of heterojunctions and provides an effective strategy for deigning efficient bidirectional Li-S catalysts in LSBs.