Scalable Production of Freestanding Few-Layer β₁₂-Borophene Single Crystalline Sheets as Efficient Electrocatalysts for Lithium–Sulfur Batteries

Abstract

Two-dimensional (2D) borophene has attracted tremendous interest due to its fascinating properties, which have potential applications in catalysts, energy storage devices, and high-speed transistors. In the past few years, borophene was theoretically predicted as an ideal electrode material for lithium− sulfur (Li−S) batteries because of its low-density, metallic conductivity, high Li-ion surface mobility, and strong interface bonding energy to polysulfide. But until now, borophene-based Li−S batteries have not yet been achieved in experiments due to the absence of a large-scale synthetic method of freestanding borophene nanostructures with a high enough structural stability, conductivity, and uniformity. Herein, we developed a lowtemperature liquid exfoliation (LTLE) method to synthesize freestanding few-layer β 12 -borophene single-crystalline sheets with a P m 6 2 ̅ symmetry in tens of milligrams. The as-synthesized 2D sheets were used as the polysulfide immobilizers and electrocatalysts of Li−S batteries. The resulting borophene-based Li− S battery delivered an extralarge areal capacity of 5.2 mAh cm −2 at a high sulfur loading of 7.8 mg cm −2 , an excellent rate performance of 8 C (@721 mAh g −1 ), and an ultralow capacity fading rate of 0.039% in 1000 cycles, outperforming commercial Li-ion batteries and many other 2D material-based Li−S batteries. Based on the density functional theory model, the excellent electrochemical performances of the borophene-based Li−S batteries should originate from the enormous enhancement of β 12 -borophene sheets for both the surface migration of the Li-ions and the adsorption energy of Li 2 S n clusters. Our results thus demonstrate a great potential for scalable production of freestanding β 12 -borophene single-crystalline sheets in future high-performance Li−S batteries.

Enhanced Polysulfide Conversion with Highly Conductive and Electrocatalytic Iodine‐Doped Bismuth Selenide Nanosheets in Lithium–Sulfur Batteries

“…[ 31–36 ] However, cathodes based on metal sulfides are generally characterized by moderate electrical conductivities, limited sulfur utilization, insufficient cycling stability, and low rate capabilities. [ 37–41 ]…”

Atomic surface modification strategy ofMXenematerials forhigh‐performancemetal sulfur batteries

“…It is undeniable that the application of Li‐S and Na‐S batteries plays tremendous roles in energy storage devices and wearable devices nowadays 39‐43 . Despite the merits of high specific capacity, low cost, high electrode efficiency and almost nontoxicity, we are still plagued by its poor rate performance, short cycle life and low coulomb efficiency 44‐47 .…”

Macroscopic Single-Phase Monolayer Borophene on Arbitrary Substrates

“…Therefore, Bo research has been notably accelerated by a development of different synthesis methods that enabled fabrication of samples suitable for experimentation. These methods include molecular beam epitaxy (MBE) from solid boron rods, [7][8][9] sonochemical exfoliation from boron powders 10,11 and chemical vapor deposition (CVD) from gaseous diborane precursor. 12,13 Synthesis efforts are often aimed at production of large-area Bo, pushing Bo research closer to applications in, e.g., supercapacitors, flexible memory devices, photodetectors and batteries.…”

“…12,13 Synthesis efforts are often aimed at production of large-area Bo, pushing Bo research closer to applications in, e.g., supercapacitors, flexible memory devices, photodetectors and batteries. 11,[14][15][16] For example, full monolayer Bo coverage has been reached on Ag(111), 17 Cu(111), 9 Cu(100) 18 and Ir(111). 13,19 Moreover, the monolayer limit has been surpassed by the synthesis of a full Bo bilayer on Ru(0001) 20 and Cu(111).…”