Core Shell Structured S@Co(OH)2 with a Carbon-Nanofiber Interlayer: A Conductive Cathode with Suppressed Shuttling Effect for High-Performance Lithium Sulfur Batteries
Core Shell Structured S@Co(OH)2 with a Carbon-Nanofiber Interlayer: A Conductive Cathode with Suppressed Shuttling Effect for High-Performance Lithium Sulfur Batteries
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具有碳纳米纤维夹层的核壳结构S@Co(OH)(2)：一种具有抑制穿梭效应的高性能锂硫电池导电阴极
DOI：
10.1021/acsami.8b20225
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发表时间：
2019-01-30
影响因子：
9.5
通讯作者：
Sun, Shi-Gang
中科院分区：
文献类型：
--
作者：
Mo, Yu-Xue;Lin, Jin-Xia;Sun, Shi-Gang
可充电锂硫电池由于其极高的能量密度而成为储存电化学能量的潜在候选者。然而，它们的实际应用受到多硫化锂的缓慢电荷转移、阻碍Li离子扩散和穿梭效应的限制。我们在这里报告了一种高性能的正极材料，其中S亚微球的质量分数为80%，被封装在可渗透的Co（OH）（2）纳米壳层中，该纳米壳层作为物理屏障防止硫和多硫化物泄漏到电解液中，并且还有助于在充电和放电过程中催化分解多硫化物。当在S@Co（OH）（2）阴极和隔膜之间引入碳纳米纤维夹层时，Li S电池的性能可以进一步显著提高。S@Co（OH）（2）正极材料具有良好的循环稳定性，在2 C下的首次放电容量为1100 mAh g（-1），可逆容量为606 mAh g（-1）。特别地，在没有LiNO 3添加剂的情况下，该S@Co（OH）（2）阴极也表现出高达85%的库仑效率，仅略低于具有LiNO 3添加剂的商业电解质的库仑效率。相关的机理研究表明，这种优异的上级性能是由于Co（OH）（2）壳层和碳-水夹层的存在，提高了内部的电导率和离子电导率，抑制了穿梭效应。基于密度泛函理论的理论模拟也被用来计算Co（OH）（2）纳米片和多硫化物之间的相互作用。结果表明，Co（OH）（2）纳米壳层不仅可以作为物理屏障捕获多硫化物，还可以吸附多硫化物并在循环过程中催化其分解，进一步有助于抑制穿梭效应。
Rechargeable lithium sulfur batteries are potential candidates for storing electrochemical energy because of their extremely high energy density. However, their practical applications are prohibited by the sluggish charge transfer, the retarding Li ion diffusion, and the shuttle effect of lithium polysulfides. We report here a high-performance cathode material in which a S submicrosphere with a mass fraction of 80% was encapsulated within a permeable Co(OH)(2) nanoshell which functions as a physical barrier preventing the sulfur and polysulfides from leaking into the electrolyte and also contributes to the catalytic decomposition of polysulfides during the charge and discharge process. When an interlayer of carbon nanofibers is introduced between the S@Co(OH)(2) cathode and the separator, the performance of the Li S batteries can be further significantly enhanced. Specifically, the S@Co(OH)(2) cathode possesses good cycling stability over 1000 cycles with an initial discharge capacity of 1100 mAh g(-1) at 2 C and a reversible capacity of 606 mAh g(-1). In particular, without the LiNO3 additive, this S@Co(OH)(2) cathode also exhibits a Coulombic efficiency as high as 85%, just a little lower than that of commercial electrolyte with LiNO3 additive. Relevant mechanistic studies revealed that such superior performances are attributed to the enhanced internal electrical and ionic conductivity and suppressed shuttling effect, owing to the presence of the Co(OH)(2) shell and the carbon-nanofiber interlayer. Theoretical simulations based on density functional theory were also carried out to figure out the interaction between the Co(OH)(2) nanosheets and the polysulfides. It revealed that the Co(OH)(2) nanoshell, rather than merely working as a physical barrier to trap the polysulfides, could also adsorb polysulfides and catalyze their decomposition during the cycling process, further helping to suppress the shuttling effect.