Graduate School of Energy, Environment, Water, and Sustainability (EEWS) and Center for Nature-inspired Technology (CNiT), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehakro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
Nano Lett. 2014 Aug 13;14(8):4418-25. doi: 10.1021/nl501383g. Epub 2014 Jul 14.
Utilizing the unparalleled theoretical capacity of sulfur reaching 1675 mAh/g, lithium-sulfur (Li-S) batteries have been counted as promising enablers of future lithium ion battery (LIB) applications requiring high energy densities. Nevertheless, most sulfur electrodes suffer from insufficient cycle lives originating from dissolution of lithium polysulfides. As a fundamental solution to this chronic shortcoming, herein, we introduce a hierarchical porous carbon structure in which meso- and macropores are surrounded by outer micropores. Sulfur was infiltrated mainly into the inner meso- and macropores, while the outer micropores remained empty, thus serving as a "barricade" against outward dissolution of long-chain lithium polysulfides. On the basis of this systematic design, the sulfur electrode delivered 1412 mAh/g sulfur with excellent capacity retention of 77% after 500 cycles. Also, a control study suggests that even when sulfur is loaded into the outer micropores, the robust cycling performance is preserved by engaging small sulfur crystal structures (S2-4). Furthermore, the hierarchical porous carbon was produced in ultrahigh speed by scalable spray pyrolysis. Each porous carbon particle was synthesized through 5 s of carrier gas flow in a reaction tube.
利用硫的理论容量高达 1675 mAh/g 的优势，锂硫（Li-S）电池被认为是未来需要高能量密度的锂离子电池（LIB）应用的有前途的实现方式。然而，大多数硫电极由于溶解的多硫化锂而循环寿命不足。作为解决这一长期缺点的根本方法，本文引入了一种具有中孔和大孔的分层多孔碳结构，这些孔被微孔包围。硫主要渗透到内部的中孔和大孔中，而外部的微孔保持为空，从而形成了阻挡长链多硫化锂向外溶解的“障碍”。基于这种系统设计，硫电极在 500 次循环后提供了 1412 mAh/g 硫的容量，容量保持率为 77%。此外，一项对照研究表明，即使将硫装入微孔中，通过小的硫晶体结构（S2-4）的参与，仍能保持稳健的循环性能。此外，通过可扩展的喷雾热解法以超高速生产分层多孔碳。在反应管中，通过 5 秒的载气流即可合成每个多孔碳颗粒。
