State Key Laboratory of Silicon Materials, Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province & School of Materials Science and Engineering, Zhejiang University , Hangzhou 310027, PR China.
Department of Chemistry, University College London , London WC1H 0AJ, United Kingdom.
ACS Appl Mater Interfaces. 2017 Mar 29;9(12):10717-10729. doi: 10.1021/acsami.7b00672. Epub 2017 Mar 14.
Porous carbon can be tailored to great effect for electrochemical energy storage. In this study, we propose a novel structured spherical carbon with a macrohollow core and a microporous shell derived from a sustainable biomass, amylose, by a multistep pyrolysis route without chemical etching. This hierarchically porous carbon shows a particle distribution of 2-10 μm and a surface area of 672 m g. The structure is an effective host of sulfur for lithium-sulfur battery cathodes, which reduces the dissolution of polysulfides in the electrolyte and offers high electrical conductivity during discharge/charge cycling. The hierarchically porous carbon can hold 48 wt % sulfur in its porous structure. The S@C hybrid shows an initial capacity of 1490 mAh g and retains a capacity of 798 mAh g after 200 cycles at a discharge/charge rate of 0.1 C. A capacity of 487 mAh g is obtained at a rate of 3 C. Both a one-step pyrolysis and a chemical-reagent-assisted pyrolysis are also assessed to obtain porous carbon from amylose, but the obtained carbon shows structures inferior for sulfur cathodes. The multistep pyrolysis and the resulting hierarchically porous carbon offer an effective approach to the engineering of biomass for energy storage. The micrometer-sized spherical S@C hybrid with different sizes is also favorable for high-tap density and hence the volumetric density of the batteries, opening up a wide scope for practical applications.
多孔碳可以通过精心设计，在电化学储能方面发挥巨大作用。在这项研究中，我们提出了一种新型结构的球形碳，它由可持续生物质直链淀粉通过多步热解路线制备，无需化学刻蚀，具有大空心核和微孔壳。这种分级多孔碳的颗粒分布为 2-10 μm，比表面积为 672 m²/g。该结构是硫在锂硫电池正极中的有效宿主，可以减少电解液中多硫化物的溶解，并在充放电循环过程中提供高导电性。分级多孔碳可以在其多孔结构中容纳 48wt%的硫。S@C 复合材料的初始容量为 1490 mAh/g，在 0.1 C 的放电/充电速率下循环 200 次后，容量保持在 798 mAh/g。在 3 C 的倍率下，可获得 487 mAh/g 的容量。我们还评估了一步热解和化学试剂辅助热解，从直链淀粉中获得多孔碳，但得到的碳的结构对硫正极不利。多步热解和由此产生的分级多孔碳为基于生物质的储能工程提供了一种有效的方法。不同尺寸的微米级 S@C 复合材料也有利于高压实密度，从而提高电池的体积密度，为实际应用提供了广阔的前景。
