Rapid, high-efficient and scalable exfoliation of high-quality boron nitride nanosheets and their application in lithium
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RACT Boron nitride nanosheets (BNNSs) have gained significant attraction in energy and environment fields because of their two-dimensional (2D) nature, large band gap and high thermal/mechanical performance. However, the current low production efficiency of high-quality BNNSs is still a bottleneck limiting their applications. Herein, based on sonication-assisted liquid-phase exfoliation, we demonstrated a rapid, high-efficient and scalable production strategy of BNNSs and documented the effects of a spectrum of exfoliation factors (e.g., ultrasonic condition, solvent and bulk material feeding) on the yield of BNNSs. A record of yield of 72.5% was achieved while the exfoliated BNNSs have few-layer and defect-free feature. Thanks to the Lewis acid sites of the boron atoms, the BNNSs can interact with the polysulfide anions in liquid electrolyte and also can facilitate the uniform lithium deposition, which finally endow a lithium-sulfur (Li-S) battery with long life. This work provides a facile and rapid strategy for large scale preparation of high-quality BNNSs, also contributes a long-life strategy for dendrite-free Li-S battery, opens new avenues of BNNSs in energy application.
KEYWORDS boron nitride nanosheets, cavitation, sonication-assisted liquid-phase exfoliation (SALPE), modified separators, lithium-sulfur batteries
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Introduction
Boron nitride nanosheets (BNNSs), two-dimensional (2D) widebandgap (~ 6 eV) nanomaterials, have received numerous attentions because of their ultrahigh thermal conductivity of 300–2,000 W·m−1·K−1 [1, 2], highly electrical insulation [3], excellent chemical/thermal stability [4] and mechanical strength [5]. Owing to the atomic-layer (single or few-layers) thickness and 2D morphology, BNNSs have been considered as ideal candidates for thermal management [6–8], high voltage insulation [9], energy storage [10, 11], and photoelectrochemical applications [12]. Despite high demand, the production of high-quality BNNSs is still limited by the low efficiency [13]. So far, significant efforts have been made to fabricate BNNSs. Typical methods include chemical vapor deposition (CVD) [14, 15], mechanical ball milling [16, 17], electrochemical exfoliation [18], hydrothermal synthesis [19], microfluidic shear peeling [20], supercritical fluid stripping [21], ion intercalating methods [22] etc. However, most of these approaches need a long production period (typically > 5 h), and/or cause imperfections of the BNNSs. In contrast, liquid phase exfoliation (LPE) is a facile technique to produce defect-free 2D nanosheets [23], and it has been used to prepare BNNSs from bulk hexagonal boron nitride (h-BN) flakes. Nevertheless, the LPE output of BNNSs from bulk h-BN is still low (typically < 0.3 g). In addition, the production also suffers Address correspondence to [email protected]
from low yield (typically < 20%), volatile of toxic organic solvents and high energy consumption [24–27]. Lithium-sulfur (Li-S) batteries have high theoretical specific capacity (1,675 mAh·g−1) and energy density (2,600
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