Engineering Solid Electrolyte Interphase for Pseudocapacitive Anatase TiO2 Anodes in Sodium‐Ion Batteries
Engineering Solid Electrolyte Interphase for Pseudocapacitive Anatase TiO2 Anodes in Sodium‐Ion Batteries
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DOI：
10.1002/adfm.201802099
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发表时间：
2018-07
影响因子：
19
通讯作者：
Zheng-Long Xu;Kyungmi Lim;Kyu‐Young Park;Gabin Yoon;W. Seong;K. Kang
中科院分区：
文献类型：
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作者：
Zheng-Long Xu;Kyungmi Lim;Kyu‐Young Park;Gabin Yoon;W. Seong;K. Kang
锐钛矿型二氧化钛因其巨大的钠存储容量和潜在的低成本，被认为是一种很有前途的钠离子电池正极之一。然而，其确切的反应机理以及表面性质和电化学性能之间的相互作用仍未阐明。用多方法分析表明，在第一次碱化过程中，二氧化钛电极经历了非晶化，在随后的循环中，非晶相表现出假电容的钠存储行为。结果还表明，伪电容钠的存储性能对固体电解质界面层的性质很敏感。首次发现，醚基电解质能够形成薄的(≈2.5 nm)和坚固的SEI层，而传统的碳酸盐基电解质可以形成厚的(≈10 nm)和不断增长的SEI层。第一原理计算表明，乙醚溶剂/离子络合物的较高最低空位分子轨道能是造成这种差异的原因。在醚基电解液中，500次循环后，0.1Ag−1放电容量为192mAhg−1，远远高于碳酸盐电解液中的容量。这项工作阐明了锐钛矿型二氧化钛的电化学沉淀机理，并为高性能阳极的界面控制策略提供了指导。
Anatase TiO2 is considered as one of the promising anodes for sodium‐ion batteries because of its large sodium storage capacities with potentially low cost. However, the precise reaction mechanisms and the interplay between surface properties and electrochemical performance are still not elucidated. Using multimethod analyses, it is herein demonstrated that the TiO2 electrode undergoes amorphization during the first sodiation and the amorphous phase exhibits pseudocapacitive sodium storage behaviors in subsequent cycles. It is also shown that the pseudocapacitive sodium storage performance is sensitive to the nature of solid electrolyte interphase (SEI) layers. For the first time, it is found that ether‐based electrolytes enable the formation of thin (≈2.5 nm) and robust SEI layers, in contrast to the thick (≈10 nm) and growing SEI from conventional carbonate‐based electrolytes. First principle calculations suggest that the higher lowest unoccupied molecular orbital energies of ether solvents/ion complexes are responsible for the difference. TiO2 electrodes in ether‐based electrolyte present an impressive capacity of 192 mAh g−1 at 0.1 A g−1 after 500 cycles, much higher than that in carbonate‐based electrolyte. This work offers the clarified picture of electrochemical sodiation mechanisms of anatase TiO2 and guides on strategies about interfacial control for high performance anodes.