2D nanocarbon-based materials with controllable pore structures and hydrophilic surface show great potential in electrochemical energy storage systems including lithium sulfur (Li-S) batteries. This paper reports a thermal exfoliation of metal-organic framework crystals with intrinsic 2D structure into multilayer graphene stacks. This family of nanocarbon stacks is composed of well-preserved 2D sheets with highly accessible interlayer macropores, narrowly distributed 7 Å micropores, and ever most polar pore walls. The surface polarity is quantified both by its ultrahigh water vapor uptake of 14.3 mmol g at low relative pressure of P/P = 0.4 and ultrafast water wetting capability in less than 10.0 s. Based on the structural merits, this series hydrophilic multilayer graphene stack is showcased as suitable model cathode host for unveiling the challenging surface chemistry issue in Li-S batteries.
The reversible formation of chemical bonds has potential for tuning multi-electron redox reactions in emerging energy-storage applications, such as lithium-sulfur batteries. The dissolution of polysulfide intermediates, however, results in severe shuttle effect and sluggish electrochemical kinetics. In this study, quinonoid imine is proposed to anchor polysulfides and to facilitate the formation of Li S /Li S through the reversible chemical transition between protonated state (NH ) and deprotonated state (N). When serving as the sulfur host, the quinonoid imine-doped graphene affords a very tiny shuttle current of 2.60 × 10 mA cm , a rapid redox reaction of polysulfide, and therefore improved sulfur utilization and enhanced rate performance. A high areal specific capacity of 3.72 mAh cm is achieved at 5.50 mA cm on the quinonoid imine-doped graphene based electrode with a high sulfur loading of 3.3 mg cm . This strategy sheds a new light on the organic redox mediators for reversible modulation of electrochemical reactions.
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