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.