Efficient Polysulfide Chemisorption in Covalent Organic Frameworks for High-Performance Lithium-Sulfur Batteries
Efficient Polysulfide Chemisorption in Covalent Organic Frameworks for High-Performance Lithium-Sulfur Batteries
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高性能锂硫电池共价有机框架中的高效多硫化物化学吸附
DOI：
10.1002/aenm.201601250
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发表时间：
2016-12-21
影响因子：
27.8
通讯作者：
Tang, Zhiyong
中科院分区：
文献类型：
--
作者：
Ghazi, Zahid Ali;Zhu, Lingyun;Tang, Zhiyong
DOI：10.1002/aenm201601250被广泛用于通过N-Li+相互作用来捕获LiPS，[4，26-28]同时，由于PS阴离子与多孔炭中正极化的硼之间的强烈相互作用，B掺杂可以改善Li-S电池中PSS/C的正极性能。[29]尽管杂原子掺杂增强了PSS在阴极中的捕获，但由于比表面积有限和掺杂率低，捕获效率仍然有限。此外，无定形多孔炭中较差的孔道有序性和较宽的孔径分布已成为阻碍硫均匀分布和再沉积的主要障碍。为了在保证硫的高比表面积和有序孔结构的同时获得高的掺杂率，Tarascon和他的同事们率先使用金属有机骨架(MOF)作为载体材料来储存硫，利用了PSS和含氧骨架之间的弱结合。此外，郑等[31]和周等[32]还报道了PSS和MOF之间的Lewis酸碱相互作用，这有助于减少穿梭效应。然而，MOF的热稳定性差和重金属中心增加了宿主密度，从而降低了电池的能量密度，限制了MOF的利用。最近，廖某等人提出了自己的观点。提出了利用低密度、小孔径、大比表面积的有机多孔材料--掺氮共价有机骨架材料(CTF-1)作为硫磺储存的载体材料。然而，由于PSS与富N孔表面之间缺乏强烈的相互作用，这种掺氮COF仅表现出中等的PSS捕集效率。考虑到COF是一种多孔材料，可以精确地控制孔的大小和表面，以及活性物种在孔中的均匀浸渍，因此有很大的机会合理地设计有效的COF作为宿主来储存硫，并完全限制可移动的氧化还原PS物种。尽管Lee和他的同事最近采用了在介孔碳纳米管上生长的微孔CoF-1的复合结构作为化学捕获Li-S电池中PSS的新夹层，但碳纳米管的引入会增加全面研究COF的电化学性质的复杂性。[34]到目前为止，正B和负O双掺杂的COF从未被用作Li-S电池的硫基质，这与层间使用是一个明显不同的概念。在此，我们建议使用硼酸酯COFS作为改进的捕集基质以增强对LiPS的吸附。孔内正极化B和负极化O的高密度和均匀分布保证了Sx2、−和Li+在可溶性LiPS中的同时吸附，从而使硫再沉积更加均匀。因此，这种新的宿主显示出前所未有的强大的吸附能力，从而有效地将LiPS捕获在阴极中。作为最有前途的储能设备之一，锂硫(Li-S)电池因其优异的理论容量(1672 mA HG−1)和比能量密度(2600WH kg−1)而备受关注。[1-4]遗憾的是，尽管Li-S电池具有巨大的潜力，但它仍存在一些缺陷，严重阻碍了其实际应用。主要是高阶多硫化锂(Li2Sx，4≤x≤8)等中间氧化还原物种在电解液中的扩散及其在阴阳极之间的自由迁移。这些都解散了…
DOI: 10.1002/aenm. 201601250 are widely used to trap LiPSs via N-Li+ interaction,[4, 26–28] meanwhile B doping is demonstrated to improve the performance of S/carbon cathode in Li-S batteries due to the strong interaction between PS anions and positively polarized boron in the porous carbon.[29] Despite the fact that heteroatom doping enhances PSs trapping in the cathodes, the trapping efficiency is still limited due to constrained surface area and low doping ratio. In addition, the poor order and broad size distribution of pores in amorphous porous carbons have become major impediment to uniform sulfur distribution and redeposition. In order to get high doping ratio while ensuring high surface area and ordered pore structure for regular sulfur distribution, Tarascon and co-workers pioneered the use of metal-organic frameworks (MOFs) as host materials for sulfur storage, taking advantage of the weak binding between the PSs and the oxygenated framework.[30] Moreover, Zheng et al.[31] and Zhou et al.[32] also reported the Lewis acid–base interactions between PSs and MOFs, which helped decreasing shuttle effect. Nevertheless, the utilization of MOFs is still limited by their poor thermal stability and heavy metal sites, which increase the density of host and thus decrease the energy density of batteries. Recently, Liao et al. proposed utilization of N-doped covalent organic framework (COF)(CTF-1), an organic porous material with low density, small pore size, and large surface area, as host material for sulfur storage.[33] However, this N-doped COF shows only moderate PSs trapping efficiency due to lack of strong interaction between PSs and N-rich pore surface. Considering COFs are porous materials that allow precise control of pore size and surface, as well as homogeneous impregnation of active species in the pores, there is great opportunity to rationally design effective COFs as hosts to store sulfur and fully confine the mobile redox PS species. Although, Lee and co-workers have recently adopted the composite structure of microporous COF-1 grown on mesoporous carbon nanotube as a new interlayer for chemical trapping of PSs in Li-S batteries, the introduction of carbon nanotubes can give rise to complexity to fully probe the electrochemical properties of COFs.[34] Till now, the positive B and negative O double doped boronate ester COFs have never been used as sulfur hosts in Li-S batteries, which is a distinctly different conception from interlayer use. Here, we suggest using boronate ester COFs as the improved trapping matrices for enhanced adsorption of LiPSs. The high density and uniform distribution of positively polarized B and negatively polarized O within the pores guarantee simultaneous adsorption of Sx 2− and Li+ in soluble LiPSs and thus render sulfur redeposition more uniform. As a result, this new host shows unprecedentedly strong adsorption ability and hence efficiently traps LiPSs within the cathodes. Such unique feature distinguishes boronate ester COF system from other N-dopedAs one of the most promising energy storage devices, lithiumsulfur (Li-S) batteries have attracted much attention due to their exceptional theoretical capacity (1672 mA hg− 1) and specific energy density (2600 Wh kg− 1) compared to state-of-the-art lithium-ion batteries (LIBs).[1–4] Unfortunately, despite their great potential, Li-S battery systems suffer from several drawbacks that severely impede the practical application. The major one is the diffusion of intermediate redox species, eg, the high-order lithium polysulfides (PSs)(Li2Sx, 4≤ x≤ 8), into the electrolyte solution and their free migration between the cathode and anode. These dissolved …