Embedding Sulfur in MOF-Derived Microporous Carbon Polyhedrons for Lithium-Sulfur Batteries
Embedding Sulfur in MOF-Derived Microporous Carbon Polyhedrons for Lithium-Sulfur Batteries
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DOI：
10.1002/chem.201301689
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发表时间：
2013-08-12
影响因子：
4.3
通讯作者：
Lou, Xiong Wen (David)
中科院分区：
文献类型：
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作者：
Wu, Hao Bin;Wei, Shuya;Lou, Xiong Wen (David)
作为一种有前途的可充电电池系统，锂硫（Li-S）电池以低成本且环保的硫作为正极材料，可以提供高达1672mAhg-1的理论比容量和2500 Whkg-1的能量密度。[1-5]虽然硫作为正极材料的潜在用途早已被发现，但一些严重的缺点阻碍了Li-S电池的实现。[2, 3]其中一个限制是硫的绝缘性质电导率极低，为 5·10-30 S cm-1，导致硫的利用率较低。另一个众所周知的问题与多硫化物（电化学反应过程中形成的中间产物）在有机电解质中的容易溶解有关。溶解的多硫化物在电极之间“穿梭”，导致库仑效率低，并在电极表面沉积高电阻层。这些有害问题导致电化学性能不令人满意且容量快速衰减。人们提出了几种方法来克服Li-S电池中的上述挑战，例如开发新型电解质和电极材料。[4-13]在这些努力中，使用含硫复合材料代替纯硫作为正极材料已被证明是实现高性能Li-S电池的有效途径。[14-22]聚合物和多孔碳是与硫形成复合材料的常见候选者，其通过物理和/或化学相互作用固定负载的硫，也可能固定衍生的多硫化物。此外，复合材料的导电性也优于用原始硫获得的导电性。特别是，多孔碳材料由于其与硫的良好相容性、易于获得以及丰富的具有不同孔隙率和结构的候选材料而引起了广泛的关注。介孔碳材料作为限制硫的主体材料已被广泛研究。[4-5,18,23]例如，由硫和有序介孔碳或介孔空心碳球组成的纳米复合材料已显示出改善的硫利用率和循环稳定性。[4,8]尽管如此，长时间循环后容量持续衰减的情况仍然常见，优化的醚基电解质的使用似乎是必不可少的。最近关于具有丰富微孔的碳材料的报道揭示了独特的特征。 [24, 25] 嵌入微孔碳中的硫在相对于 Li+/Li 约 1.8 V 的较低电势下表现出明显的放电平台，这与典型硫阴极的两个平台不同。更重要的是，这些微孔碳/硫纳米复合材料通常在循环时表现出出色的容量保持率，并且与传统碳酸酯基电解质具有良好的相容性。然而，微孔碳的独特特性的起源尚不完全清楚。近年来，由金属有机骨架（MOF）或多孔配位聚合物（PCP）合成多孔碳材料由于制备过程简便、碳产率高和独特的多孔结构而受到越来越多的关注。[26-30]例如，MOF-5与糠醇的碳化产生纳米孔碳，表现出优异的超级电容性能。[26]由铝基 PCP 制备的具有纤维状形貌的碳材料表现出非常高的孔隙率。 [29]特别是，MOF 和 PCP 作为微孔碳制造的模板和前体非常有吸引力。与许多其他高孔隙碳相比......
As a promising rechargeable battery system, lithium–sulfur (Li–S) batteries can deliver an exceptionally high theoretical specific capacity of 1672mAhgÀ1 and an energy density of 2500 WhkgÀ1 with the low-cost and environmentfriendly sulfur as the cathode material.[1–5] Although the potential use of sulfur as a cathode material has long been discovered, several severe drawbacks have hindered the realization of Li–S batteries.[2, 3] One limitation is the insulating nature of sulfur with a very low conductivity of 5 10À30 S cmÀ1, which results in low utilization of sulfur. Another well-known problem is associated with the easy dissolution of polysulfides, the intermediate products formed during the electrochemical reaction, in organic electrolytes. The dissolved polysulfides “shuttle” between the electrodes, leading to the low Coulombic efficiency and deposition of a highly resistive layer on the surface of electrodes. These detrimental issues result in unsatisfactory electrochemical performance with rapid fading of capacity. Several approaches have been proposed to overcome the above-mentioned challenges in Li–S batteries, such as developing novel electrolytes and electrode materials.[4–13] Among these efforts, using sulfur-containing composites instead of pure sulfur as the cathode materials has been demonstrated as an effective way towards high-performance Li–S batteries.[14–22] Polymers and porous carbons are the common candidates to form composites with sulfur, which immobilize the loaded sulfur, and probably also the derived polysulfides via physical and/or chemical interactions. In addition, the electrical conductivity of composite materials is also better than that obtained with pristine sulfur. In particular, porous carbon materials have attracted intensive attention due to their good compatibility with sulfur, easy accessibility, and the abundance of candidates with diverse porosity and structures. Mesoporous carbon materials have been widely studied as the host materials to confine sulfur.[4–5, 18, 23] For example, nanocomposites consisting of sulfur and ordered mesoporous carbon or mesoporous hollow carbon spheres have shown improved sulfur utilization and cycling stability.[4, 8] Nonetheless, continuous capacity fading upon prolonged cycling is still commonly observed, and the use of optimized ether-based electrolytes seems to be indispensable. Recent reports on carbon materials with rich micropores have revealed distinct characteristics.[24, 25] Sulfur embedded in microporous carbon shows a pronounced discharge plateau at a lower potential of about 1.8 V versus Li+/Li, which is different from the two plateaus of a typical sulfur cathode. More importantly, these microporous carbon/sulfur nanocomposites generally show outstanding capacity retention upon cycling and good compatibility with conventional carbonate-based electrolytes. However, the origins of the unusual characteristics of microporous carbon are not fully understood yet.In recently years, syntheses of porous carbon materials from metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) have attracted growing attention due to the facile preparation procedures, high carbon yield, and unique porous structures.[26–30] For example, carbonization of MOF-5 with furfuryl alcohol results in nanoporous carbon, which shows excellent supercapacitive performance.[26] The carbon materials with fiber-like morphology prepared from Al-based PCPs exhibit remarkably high porosity.[29] In particular, MOFs and PCPs are very attractive as both the template and the precursor for the fabrication of microporous carbon. Compared with many other highly porous carbon …