Han Zhiyuan, Li Xueying, Li Qiang, Li Hongsen, Xu Jie, Li Na, Zhao Guoxia, Wang Xia, Li Hongliang, Li Shandong
College of Physics, University-Industry Joint Center for Ocean Observation and Broadband Communication, Qingdao University, Qingdao 266071, China.
School of Sciences, Hebei University of Science and Technology, Shijiazhuang 050018, China.
ACS Appl Mater Interfaces. 2021 Feb 10;13(5):6265-6275. doi: 10.1021/acsami.0c20721. Epub 2021 Jan 27.
Polyoxometalate (POM) as an "electronic sponge" can store a great number of electrons; however, shortcomings of poor conductivity and solubility in electrolytes cause a significant decrease in specific capacity and poor rate capability. To address the aforementioned disadvantages, a dual strategy was proposed, including coating the conductive polypyrrole (PPy) and utilizing nitrogenous ligands (1,10-phenanthroline monohydrate = 1,10-phen) for metal-organic frameworks (MOFs) to fabricate a [Cu(1,10-phen)(HO)][MoO]@PPy (Cu-POMOF@PPy) composite, effectively confining the POM in MOFs to avoid dissolution of POM in the electrolyte and improve electrochemical stability. Simultaneously, the PPy shell could improve the conductivity, contribute extra capacity, and alleviate volume variation of Cu-POMOF during cycling. Therefore, the final Cu-POMOF@PPy composite provides an excellent specific capacity of around 769 mA h g at 0.1 A g after 160 cycles and good rate performance, associated with great cycling stability (319 mA h g at 2 A g after 500 cycles). Moreover, the electrochemical reaction mechanism of Cu-POMOF@PPy was investigated by XPS measurements, indicating that storage of electrons results from the reduction/oxidation of Mo atoms (Mo ↔ Mo) and Cu atoms (Cu ↔ Cu). As a consequence, this work not only proposes a novel method for preparing POM-based lithium-ion batteries but also expands the variety of anode materials.
多金属氧酸盐（POM）作为一种“电子海绵”，能够存储大量电子；然而，其导电性差以及在电解质中溶解度低的缺点导致比容量显著下降且倍率性能不佳。为了解决上述缺点，提出了一种双重策略，包括包覆导电聚吡咯（PPy）以及利用含氮配体（一水合1,10 - 菲啰啉 = 1,10 - phen）制备金属有机框架（MOF），以构建[Cu(1,10 - phen)(HO)][MoO]@PPy（Cu - POMOF@PPy）复合材料，有效地将POM限制在MOF中，避免POM在电解质中溶解并提高电化学稳定性。同时，PPy壳层可以提高导电性、贡献额外容量并减轻Cu - POMOF在循环过程中的体积变化。因此，最终的Cu - POMOF@PPy复合材料在160次循环后，在0.1 A g下提供约769 mA h g的优异比容量和良好的倍率性能，以及出色的循环稳定性（在2 A g下500次循环后为319 mA h g）。此外，通过XPS测量研究了Cu - POMOF@PPy的电化学反应机理，表明电子存储源于Mo原子（Mo ↔ Mo）和Cu原子（Cu ↔ Cu）的还原/氧化。因此，这项工作不仅提出了一种制备基于POM的锂离子电池的新方法，还扩展了阳极材料的种类。
