The electrochemical performance of lithium-sulfur(Li-S)batteries is strongly hampered by the shuttle effect and slow redox kinetics of lithium polysulfides(Li PSs).Surface modified interlayer of a separator of Li-S ba...The electrochemical performance of lithium-sulfur(Li-S)batteries is strongly hampered by the shuttle effect and slow redox kinetics of lithium polysulfides(Li PSs).Surface modified interlayer of a separator of Li-S batteries is demonstrated to be an effective strategy to overcome this problem.Herein,cobalt nanoparticles confined in nitrogen co-doped porous carbon framework(Co-CN)were developed from pyrolysis of ZIF-67 and used as interlayer of PP separator for Li-S batteries,and were functionalized by four pyrrole derivatives,1-phenylpyrrole,1-methyl pyrrole,1-(p-toluenesulfonyl)pyrrole,and 1-pyrrole,respectively,which were screened in terms of the electron-withdrawing/donating ability of the substituent groups on the pyrrolic nitrogen.The impact of the molecular structure of pyrrole derivatives on the interaction with Li PSs and the electrochemical performance of Li-S batteries were explored by nuclear magnetic resonance and theoretical calculation.It is uncovered that 1-phenylpyrrole shows the highest enhancement of redox kinetics of Li PSs,attributing to the optimal interaction with Co nanoparticles and Li PSs.Therefore,1-phenylpyrrole modified Co-CN interlayer enables the best electrochemical performance for the Li-S batteries,delivering a specific capacity of 562 m Ah g^(-1)at 5 C and a capacity of 538,526,and 449 m Ah g^(-1)after 500 cycles at 1,2,and 3 C,respectively.At a high sulfur loading of 5.5 mg cm^(-2),it achieves a capacity of 440 m Ah g^(-1)after 500 cycles at 1 C.This work reveals the interaction mechanism among Li PSs,Co nanoparticles and the molecular modifiers in improving the electrochemical performance of Li-S batteries.展开更多
Under the catalysis of Yb(OTf)3, nucleophilic conjugate addition of pyrrole to electron deficient olefins in CH2Cl2 at ambient temperature gives corresponding 2-alkylated pyrrole derivatives in good yields with high s...Under the catalysis of Yb(OTf)3, nucleophilic conjugate addition of pyrrole to electron deficient olefins in CH2Cl2 at ambient temperature gives corresponding 2-alkylated pyrrole derivatives in good yields with high selectivity.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2017YFA0206703)the National Natural Science Foundation of China(Grant No.U2032151)。
文摘The electrochemical performance of lithium-sulfur(Li-S)batteries is strongly hampered by the shuttle effect and slow redox kinetics of lithium polysulfides(Li PSs).Surface modified interlayer of a separator of Li-S batteries is demonstrated to be an effective strategy to overcome this problem.Herein,cobalt nanoparticles confined in nitrogen co-doped porous carbon framework(Co-CN)were developed from pyrolysis of ZIF-67 and used as interlayer of PP separator for Li-S batteries,and were functionalized by four pyrrole derivatives,1-phenylpyrrole,1-methyl pyrrole,1-(p-toluenesulfonyl)pyrrole,and 1-pyrrole,respectively,which were screened in terms of the electron-withdrawing/donating ability of the substituent groups on the pyrrolic nitrogen.The impact of the molecular structure of pyrrole derivatives on the interaction with Li PSs and the electrochemical performance of Li-S batteries were explored by nuclear magnetic resonance and theoretical calculation.It is uncovered that 1-phenylpyrrole shows the highest enhancement of redox kinetics of Li PSs,attributing to the optimal interaction with Co nanoparticles and Li PSs.Therefore,1-phenylpyrrole modified Co-CN interlayer enables the best electrochemical performance for the Li-S batteries,delivering a specific capacity of 562 m Ah g^(-1)at 5 C and a capacity of 538,526,and 449 m Ah g^(-1)after 500 cycles at 1,2,and 3 C,respectively.At a high sulfur loading of 5.5 mg cm^(-2),it achieves a capacity of 440 m Ah g^(-1)after 500 cycles at 1 C.This work reveals the interaction mechanism among Li PSs,Co nanoparticles and the molecular modifiers in improving the electrochemical performance of Li-S batteries.
文摘Under the catalysis of Yb(OTf)3, nucleophilic conjugate addition of pyrrole to electron deficient olefins in CH2Cl2 at ambient temperature gives corresponding 2-alkylated pyrrole derivatives in good yields with high selectivity.
