Lithium–sulfur
batteries (LSBs) have been considered promising
candidates for application in high-density energy storage systems
owing to their high gravimetric and volumetric energy densities. However,
LSB technology faces many barriers from the intrinsic properties of
active materials that need to be solved to realize high-performance
LSBs. Herein, an aqueous binder, that is, PPCP, based on polyethyleneimine
(PEI), polyvinylpyrrolidone (PVP), citric acid (CA), and polyethylene
oxide (PEO), was developed. The synthesized PPCP binder has incredible
mechanical properties, suitable viscosity, and essential functional
groups for developing an effective and reliable LSB system. This study
demonstrates that CA is crucial in cross-linking PEI–PVP polymer
molecules, and PEO segments significantly enhance the flexibility
of the PPCP binder; thus, the binder can mechanically stabilize the
cathode structure over many operating cycles. The redistribution of
active materials during the charge–discharge processes and
reduction of the shuttle effect originate from the excellent chemical
interactions of PPCP with lithium polysulfides, which is confirmed
by the density functional theory calculation, enabling an ultra-long
electrochemical cycle life of 1800 cycles with a low decay rate of
0.0278% cycle–1.
Using zeolite as a heterogeneous catalyst, the reaction conditions were optimized to increase the yield and selectivity of diglycerol (DG) and triglycerol (TG) in the direct etherification reaction of glycerol. By the addition of weakly acidic alkali metal-based inorganic salts (NaHSO4 and KHSO4), the selectivities and yields of DG and TG increased. Although the conversion of glycerol was lowered due to the role of the additive as an inhibitor, the reaction conditions were optimized by controlling the amounts and reaction times of the additives to increase the yields of DG and TG. Under the optimized condition, the glycerol conversion was as high as 85.4%, and the highest yields of DG and TG were observed as 54.1% and 21.3%, respectively. The recyclability of the catalysts was much enhanced by the influence of the additives suppressing the formation of oligomers.
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