Prussian Blue: A Potential Material to Improve the Electrochemical Performance of Lithium–Sulfur Batteries

The Prussian blue, as a potential adsorbent of polysulfides to suppress the dissolution and shuttle of polysulfides for lithium–sulfur batteries, has been studied in this work. Our results show that Prussian blue improves the electrochemical reaction kinetics during discharge/charge processes. More importantly, the cathode with Prussian blue exhibits better cycling stability and higher discharge capacity retention (722 mAh g^–1 at 0.2 A g^–1 after 100 cycles) than the one without Prussian blue (151 mAh g^–1). These improvements of electrochemical performances are ascribed to the fact that Prussian blue is very effective in suppressing the dissolution of polysulfides into liquid electrolyte by chemical adsorption

Directly Coating a Multifunctional Interlayer on the Cathode via Electrospinning for Advanced Lithium–Sulfur Batteries

The lithium–sulfur battery is considered as a prospective candidate for a high-energy-storage system because of its high theoretical specific capacity and energy. However, the dissolution and shutter of polysulfides lead to low active material utilization and fast capacity fading. Electrospinning technology is employed to directly coat an interlayer composed of polyacrylonitrile (PAN) and nitrogen-doped carbon black (NC) fibers on the cathode. Benefiting from electrospinning technology, the PAN-NC fibers possess good electrolyte infiltration for fast lithium-ion transport and great flexibility for adhering on the cathode. The NC particles provide good affinity for polysufides and great conductivity. Thus, the polysulfides can be trapped on the cathode and reutilized well. As a result, the PAN-NC-coated sulfur cathode (PAN-NC@cathode) exhibits the initial discharge capacity of 1279 mAh g^–1 and maintains the reversible capacity of 1030 mAh g^–1 with capacity fading of 0.05% per cycle at 200 mA g^–1 after 100 cycles. Adopting electrospinning to directly form fibers on the cathode shows a promising application

Investigation of the Na Storage Property of One-Dimensional Cu_2–<i>x</i>Se Nanorods

In this study, one-dimensional Cu_2–<i>x</i>Se nanorods synthesized by a simple water evaporation-induced self-assembly approach are served as the anode material for Na-ion batteries for the first time. Cu_2–<i>x</i>Se electrodes express outstanding electrochemical properties. The initial discharge capacity is 149.3 mA h g^–1 at a current density of 100 mA g^–1, and the discharge capacity can remain at 106.2 mA h g^–1 after 400 cycles. Even at a high current density of 2000 mA g^–1, the discharge capacity of the Cu_2–<i>x</i>Se electrode still remains at 62.8 mA h g^–1, showing excellent rate performance. Owing to the excellent electronic conductivity and one-dimensional structure of Cu_2–<i>x</i>Se, the Cu_2–<i>x</i>Se electrodes manifest fast Na⁺ ion diffusion rate. Moreover, detailed Na⁺ insertion/extraction mechanism is further investigated by ex situ measurements and theoretical calculations

Hexagonal Boron Nitride with Designed Nanopores as a High-Efficiency Membrane for Separating Gaseous Hydrogen from Methane

Using first-principles calculations and molecular dynamics simulations, we theoretically explored the potential applications of hexagonal boron nitride (h-BN) for H₂/CH₄ separation. The h-BN with appropriate pores possesses excellent H₂/CH₄ selectivity (>10⁵ at room temperature). Furthermore, the adsorption energies (0.1 eV more or less) of both H₂ and CH₄ on the designed monolayer membranes are sufficiently low to prevent the blocking of the nanopores in a realistic separating process. Particularly, we demonstrate a highly promising membrane (h-BN with a triangular pore and a N9H9 rim) with a calculated diffusion barrier of 0.01 eV for H₂ diffusion, and the simulated flux of H₂ across the single layer is as large as 4.0 × 10⁷ GPU at 300 K. Additionally, the estimated permeability of H₂ significantly exceeds the industrially accepted standard for gas separation over a broad temperature range. Therefore, our results suggest that porous boron nitride nanosheets will be applicable as new membranes for gas separation

Mechanism on the Improved Performance of Lithium Sulfur Batteries with MXene-Based Additives

The loss of sulfur in the cathode of a lithium sulfur battery (LSB) severely hinders the practical application of LSBs, and so do the insulativity of S and its lithiation end products. The incorporation of MXene can significantly improve the performance of LSBs; however, the underlying mechanism at the atomic scale has not been deeply explored. In the present work, by using density functional theory calculations, we systemically studied the interactions of lithium (poly)­sulfides (Li₂S_<i>m</i>) on Ti-based bare MXenes (Ti_<i>n</i>X_<i>n</i>–1) and surface functionalized Ti₂C with −F, −O, and −OH groups. Through analyzing the geometric and electronic structures, binding energies, and deformation charge densities of Li₂S_<i>m</i> adsorbed MXenes, we found that the strong Ti–S bonds dominate the interactions between Li₂S<i>_m</i> and MXenes. The strong Coulombic interactions help cathodes to confine S from dissolution. Besides, the conductivities of MXenes and Li₂S<i>_m</i>@MXenes are beneficial for the overall performance of the LSB. These will provide in-depth theoretical guidance support for the utilization of MXene in LSBs