Watermelon Flesh-Like Ni3 S2 @C Composite Separator with Polysulfide Shuttle Inhibition for High-Performance Lithium-Sulfur Batteries.

The shuttle effect limits the practical application of lithium-sulfur (Li-S) batteries with high specific capacity and cheap price. Herein, a three-dimensional carbon substrate containing Ni3 S2 nanoparticles is created to modify the separator. The in situ optical visualization battery proves that the material can realize the rapid conversion of Li2 S6 . Moreover, the impact of lithium-ion diffusion on the reactions in the cell is investigated, and the mechanism of Ni3 S2 @C in the cell is proposed based on the "adsorption-diffusion-conversion" mechanism. The "adsorption-diffusion-conversion" process of polysulfide is carried out on the surface of the composite separator, showing positive effects on the inhibition of polysulfide shuttle and the promotion of conversion. The separator is modified to improve sulfur utilization and reduce dead sulfur accumulation through a strategy of chemical immobilization and physical blocking. This helps to bridge the existing gaps of Li-S batteries.

Molecular Bridges Stabilize Graphene Oxide Membranes in Water.

Recent innovations highlight the great potential of two-dimensional graphene oxide (GO) films in water-related applications. However, undesirable water-induced effects, such as the redispersion and peeling of stacked GO laminates, greatly limit their performance and impact their practical application. It remains a great challenge to stabilize GO membranes in water. A molecular bridge strategy is reported in which an interlaminar short-chain molecular bridge generates a robust GO laminate that resists the tendency to swell. Furthermore, an interfacial long-chain molecular bridge adheres the GO laminate to a porous substrate to increase the mechanical strength of the membrane. By rationally creating and tuning the molecular bridges, the stabilized GO membranes can exhibit outstanding durability in harsh operating conditions, such as cross-flow, high-pressure, and long-term filtration. This general and scalable stabilizing approach for GO membranes provides new opportunities for reliable two-dimensional laminar films used in aqueous environments.

Facile Synthesis of a SiOx-Graphite Composite toward Practically Accessible High-Energy-Density Lithium-Ion Battery Anodes.

SiOx-based material is a promising candidate for lithium-ion batteries (LIBs) owing to its high theoretical capacity. The inherent disadvantages of poor electronic conductivity and large volume variation can be solved by constructing the outermost carbon layer and reserving internal voids. However, the practical application of SiOx/C composites remains a great challenge due to the unsatisfactory energy density. Herein, we propose a facile synthetic approach for fabricating SNG/H-SiOx@C composites, which are constructed by amorphous carbon, hollow SiOx (H-SiOx), and spherical natural graphite (SNG). H-SiOx alleviates volume expansion, while amorphous carbon promotes Li+ migration and stable solid electrolyte interphase (SEI) formation. The as-prepared SNG/H-SiOx@C demonstrates a high reversible capacity (465 mAh g-1), excellent durability (93% capacity retention at 0.5C after 500 cycles), lower average delithiation potential than SNG (0.143 V after 500 cycles), and a 14% gravimetric energy density improvement at a loading level of 4.5 mg cm-2. Even at a compacted density of 1.5 g cm-3, the SNG/H-SiOx@C anode presents a modest volume deformation of 14.3% after 100 cycles at 0.1C.

In situ synthesis of VS4/Ti3C2Tx MXene composites as modified separators for lithium-sulfur battery.

Lithium-sulfur (Li-S) batteries are regarded as highly prospective energy storage devices. However, problems such as low sulfur utilization, poor cycle performance, and insufficient rate capability hinder the commercial development of Li-S batteries. Three-dimensional (3D) structure materials have been applied to modify the separator of Li-S batteries to suppress the diffusion of lithium polysulfides (LiPSs) and inhibit the transmembrane diffusion of Li+. A vanadium sulfide/titanium carbide (VS4/Ti3C2Tx) MXene composite with a 3D conductive network structure has been synthesized in situ by a simple hydrothermal reaction. VS4 is uniformly loaded on the Ti3C2Tx nanosheets through vanadium-carbon(V-C) bonds, which effectively inhibits the self-stacking of Ti3C2Tx. The synergistic action of VS4 and Ti3C2Tx substantially reduces the shuttle of LiPSs, improves interfacial charge transfer, and boosts the kinetics of LiPSs conversion, consequently increasing the rate performance and cycle stability of the battery. The assembled battery has a specific discharge capacity of 657 mAhg-1 after 500 cycles at 1C, with a high capacity retention rate of 71%. The construction of VS4/Ti3C2Tx composite with a 3D conductive network structure provides a feasible strategy for the application of polar semiconductor materials in Li-S batteries. It also provides an effective solution for the design of high-performance Li-S batteries.

Hollow Structure Co1-xS/3D-Ti3C2Tx MXene Composite for Separator Modification of Lithium-Sulfur Batteries.

The commercial application of lithium-sulfur (Li-S) batteries has faced obstacles, including challenges related to low sulfur utilization, structural degradation resulting from electrode volume expansion, and migration of polysulfide lithium (LiPSs). Herein, Co1-xS/3D-Ti3C2Tx composites with three-dimensional (3D) multilayered structures are used as separator modification materials for Li-S batteries to solve these problems. The multilevel layered structure of Co1-xS/3D-Ti3C2Tx establishes an efficient electron and Li+ transfer path, alleviates the volume change during the battery charge-discharge process, and enhances the stability of the structure. In addition, the battery assembled with the modified separator shows excellent discharge capacity and cycle stability at 0.5 C and could maintain a high discharge capacity after 500 cycles. This work provides a method for designing highly dispersed metal sulfide nanoparticles on MXenes and extends the application of MXenes-based composites in electrochemical energy storage.

Novel ZIF-300 Mixed-Matrix Membranes for Efficient CO2 Capture.

Because of the high separation performance and easy preparation, mixed-matrix membranes (MMMs) consisting of metal-organic frameworks have received much attention. In this article, we report a novel ZIF-300/PEBA MMM consisting of zeolite imidazolate framework (ZIF-300) crystals and polyether block amide (PEBA) matrix. The ZIF-300 crystal size was effectively reduced by optimizing the hydrothermal reaction condition from ∼15 to ∼1 µm. The morphology and physicochemical and sorption properties of the synthesized ZIF-300 crystals and as-prepared ZIF-300/PEBA MMMs were systematically studied. The results showed that ZIF-300 crystals with a size of ∼1 µm maintained excellent preferential CO2 sorption over N2 without degradation of the crystal structure in the MMMs. As a result, uniformly incorporated ZIF-300 crystals highly enhanced both the CO2 permeability and the CO2/N2 selectivity of pure PEBA membrane. The optimized ZIF-300-PEBA MMMs with a ZIF-300 loading of 30 wt % exhibited a high and stable CO2 permeability of 83 Barrer and CO2/N2 selectivity of 84, which are 59.2% and 53.5% higher than pure PEBA membrane, respectively. The obtained performance surpassed the upper bound of state-of-the-art membranes for CO2/N2 separation. This work demonstrated that the proposed ZIF-300/PEBA MMM could be a potential candidate for an efficient CO2 capture process.