Grapevine-like high entropy oxide composites boost high-performance lithium sulfur batteries as bifunctional interlayers

Lithium-sulfur batteries(LSBs)with high energy densities have been demonstrated the potential for energy-intensive demand applications.However,their commercial applicability is hampered by hysteretic electrode reaction kinetics and the shuttle effect of lithium polysulfides(LiPSs).In this work,an interlayer consisting of high-entropy metal oxide(Cu_(0.7)Fe_(0.6)Mn_(0.4)Ni_(0.6)Sn_(0.5))O_(4) grown on carbon nanofibers(HEO/CNFs)is designed for LSBs.The CNFs with highly porous networks provide transport pathways for Li^(+) and e^(-),as well as a physical sieve effect to limit LiPSs crossover.In particular,the grapevine-like HEO nanoparticles generate metal-sulfur bonds with LiPSs,efficiently anchoring active materials.The unique structure and function of the interlayer enable the LSBs with superior electrochemical performance,i.e.,the high specific capacity of 1381 mAh g^(-1) at 0.1 C and 561 mAh g^(-1) at 6 C.This work presents a facile strategy for exploiting high-performance LSBs.

Natural tea-leaf-derived, ternary-doped 3D porous carbon as a high-performance electrocatalyst for the oxygen reduction reaction

To commercialize fuel cells and metal-air batteries, cost-effective, highly active catalysts for the oxygen reduction reaction （ORR） must be developed. Herein, we describe the development of low-cost, heteroatom （N, P, Fe） ternary-doped, porous carbons （HDPC）. These materials are prepared by one-step pyrolysis of natural tea leaves treated with an iron salt, without any chemical and physical activation. The natural structure of the tea leaves provide a 3D hierarchical porous structure after carbonization. Moreover, heteroatom containing organic compounds in tea leaves act as precursors to functionalize the resultant carbon frameworks. In addition, we found that the polyphenols present in tea leaves act as ligands, reacting with Fe ions to form coordination compounds; these complexes acted as the precursors for Fe and N active sites. After pyrolysis, the as-prepared HDPC electrocatalysts, especially HDPC-800 （pyrolyzed at 800℃）, had more positive onsets, half-wave potentials, and higher catalytic activities for the ORR, which proceeds via a direct four-electron reaction pathway in alkaline media, similar to commercial Pt/C catalysts. Furthermore, HDPC-X also showed enhanced durability and better tolerance to methanol crossover and CO poisoning effects in comparison to commercial Pt/C, making them promising alternatives for state-of-the-art ORR electrocatalysts for electrochemical energy conversion. The method used here provides valuable guidelines for the design of high-performance ORR electrocatalysts from natural sources at the industrial scale.