Efficient Sulfur Host Based on Yolk-Shell Iron Oxide/Sulfide-Carbon Nanospindles for Lithium-Sulfur Batteries

Tix+ in-situ intercalation and interlayer modification via titanium foil/vanadium ion solution interface of VO2.375 as sulfur-wrapped matrix enabling long-life lithium sulfur battery

Lithium sulfur battery (LSB) has great potential as a promising next-generation energy storage system owing to ultra-high theoretical specific capacity and energy density. However, the polysulfide shuttle effect and slow redox kinetics are recognized the most stumbling blocks on the way of commercializing LSB. On this account, for the first time, we use Tix+ in-situ intercalation strategy via titanium foil/vanadium ion (V5+) solution interface to modify the layer of vanadium oxide for long cycle LSB. The inserted Tix+ strengthens interlayer interaction and enhances lithium-ion mobility rate. Meanwhile, based on density functional theory (DFT) calculation, the mixed valence of V5+/V4+ in the vanadium oxide structure reduces the stress and strain of lithium-ion intercalation through the interlayer support of titanium ions (Tix+). Also, Tix+ refines the structural stability of the sulfur wrapped composite matrix so as to facilitate the LiPSs transformation, and improve the electrochemical performances. Consequently, the Ti-VO2.375/S cathode delivers a lower capacity decay of 0.037 % per cycle over 1500 cycles with a stable coulombic efficiency around 100 %.

Nickel Oxide Decorated Halloysite Nanotubes as Sulfur Host Materials for Lithium-Sulfur Batteries

Lithium-sulfur batteries with high energy density still confront many challenges, such as polysulfide dissolution, the large volume change of sulfur, and fast capacity fading in long-term cycling. Herein, a naturally abundant clay material, halloysite, is introduced as a sulfur host material in the cathode of Li-S batteries. Nickel oxide nanoparticles are embedded into the halloysite nanotubes (NiO@Halloysite) by hydrothermal and calcination treatment to improve the affinity of halloysite nanotubes to polysulfides. The NiO@Halloysite composite loaded with sulfur (S/NiO@Halloysite) is employed as the cathode of Li-S batteries, which combines the physical confinements of tubular halloysite particles and good chemical adsorption ability of NiO. The S/NiO@Halloysite electrode exhibits a high discharge capacity of 1205.47 mAh g^-1 at 0.1 C. In addition, it demonstrates enhanced cycling stability, retaining ≈60% of initial capacity after 450 cycles at 0.5 C. The synthesized NiO@Halloysite can provide a promising prospect and valuable insight into applying natural clay materials in Li-S batteries.

Mixed Cu-Fe Sulfides Derived from Polydopamine-Coated Prussian Blue Analogue as a Lithium-Ion Battery Electrode

Batteries employing transition-metal sulfides enable high-charge storage capacities, but polysulfide shuttling and volume expansion cause structural disintegration and early capacity fading. The design of heterostructures combining metal sulfides and carbon with an optimized morphology can effectively address these issues. Our work introduces dopamine-coated copper Prussian blue (CuPB) analogue as a template to prepare nanostructured mixed copper-iron sulfide electrodes. The material was prepared by coprecipitation of CuPB with in situ dopamine polymerization, followed by thermal sulfidation. Dopamine controls the particle size and favors K-rich CuPB due to its polymerization mechanism. While the presence of the coating prevents particle agglomeration during thermal sulfidation, its thickness demonstrates a key effect on the electrochemical performance of the derived sulfides. After a two-step activation process during cycling, the C-coated KCuFeS₂ electrodes showed capacities up to 800 mAh/g at 10 mA/g with nearly 100% capacity recovery after rate handling and a capacity of 380 mAh/g at 250 mA/g after 500 cycles.

Synergistic Effect between Monodisperse Fe3O4 Nanoparticles and Nitrogen-Doped Carbon Nanosheets to Promote Polysulfide Conversion in Lithium-Sulfur Batteries

Effective fabrication of electrocatalysts active in anchoring and converting lithium polysulfides is critical for the manufacturing of high-performance lithium-sulfur batteries (LSBs). In this study, original Fe₃O₄ nanospheres with diameters close to 12 nm were finely dispersed over a porous nitrogen-doped carbon matrix by the freeze-drying method to produce a three-dimensional composite material (nano-Fe₃O₄/PNC) suitable for application as a sulfur host in LSBs. Nano-Fe₃O₄/PNC loaded with sulfur (S@nano-Fe₃O₄/PNC) was used as a cathode in a Li-S cell, whose initial discharge specific capacity reached 1256 mA h g^-1 at a 0.1 C rate. After 100 charge-discharge cycles at a 0.2 C rate, the reversible capacity of S@nano-Fe₃O₄/PNC remained at 745 mA h g^-1, demonstrating a capacity retention rate of 70%. Importantly, a high Coulombic efficiency of more than 99% was achieved, indicating effective inhibition of the polysulfides' "shuttle effect" by nano-Fe₃O₄/PNC. The use of electrolytes containing lithium nitrate further reduces the "shuttle effect" of polysulfides. This study demonstrates the synergistic effect between metal oxide nanoparticles and N-doped carbon, which plays an important role in promoting the adsorption and conversion of polysulfides in LSBs.

Template-synthesis of a poly(ionic liquid)-derived Fe1-x S/nitrogen-doped porous carbon membrane and its electrode application in lithium-sulfur batteries

This study deals with the facile synthesis of Fe1-x S nanoparticle-containing nitrogen-doped porous carbon membranes (denoted as Fe1-x S/N-PCMs) via vacuum carbonization of hybrid porous poly(ionic liquid) (PIL) membranes, and their successful use as a sulfur host material to mitigate the shuttle effect in lithium-sulfur (Li-S) batteries. The hybrid porous PIL membranes as the sacrificial template were prepared via ionic crosslinking of a cationic PIL with base-neutralized 1,1'-ferrocenedicarboxylic acid, so that the iron source was molecularly incorporated into the template. The carbonization process was investigated in detail at different temperatures, and the chemical and porous structures of the carbon products were comprehensively analyzed. The Fe1-x S/N-PCMs prepared at 900 °C have a multimodal pore size distribution with a satisfactorily high surface area and well-dispersed iron sulfide nanoparticles to physically and chemically confine the LiPSs. The sulfur/Fe1-x S/N-PCM composites were then tested as electrodes in Li-S batteries, showing much improved capacity, rate performance and cycle stability, in comparison to iron sulfide-free, nitrogen-doped porous carbon membranes.