Shi Zhaoliang, Zhang Qing, Zhao Liyun, Wang Hua, Zhou Wei
School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing 100191, China.
Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China.
ACS Appl Mater Interfaces. 2020 Apr 1;12(13):15043-15052. doi: 10.1021/acsami.9b21592. Epub 2020 Mar 4.
The volume variation of electrode materials will lead to poor cyclability of lithium-ion batteries during the lithiation/delithiation process. Instead, inner-stress fragmentation is creatively used to change carbon-layer-capped FeO particles ∼30 nm in diameter into high-density FeO dots ∼4 nm in size embedded in ultrathin carbon layers. The optimized structure shows a remarkable 45.2% enhancement of lithium storage from 804.7 (the 10th cycle) to 1168.7 mA h g (the 250th cycle) at 500 mA g, even retaining 1239.5 mA h g after another 550 cycles. The electrochemical measurements reveal the enhanced capacitive behavior of the high-density FeO dots@C layers, which have more extra active sites for the insertion/extraction of Li ions, confirmed by the differential capacity plots, leading to remarkably increased specific capacity during cycling. The restructured electrode also shows a superior rate capacity and excellent cycling stability (938.7 and 815.4 mA h g over 2000 cycles at 1000 and 2000 mA g, respectively). X-ray photoelectron spectroscopy and transmission electron microscopy characterizations show that the optimized structure has stable structural and componential stability even at large rates. This work presents an MOF-guided synthesis of high-density FeO-dots' anode material optimized by inner-stress fragmentation, showing a feasible route to design high-efficiency electrode materials.
电极材料的体积变化会导致锂离子电池在锂化/脱锂过程中的循环性能较差。相反，内应力破碎被创造性地用于将直径约30 nm的碳层包覆的FeO颗粒转变为尺寸约4 nm的高密度FeO点，这些点嵌入超薄碳层中。优化后的结构在500 mA g的电流密度下，储锂性能从第10次循环时的804.7 mA h g显著提高到第250次循环时的1168.7 mA h g，提高了45.2%，甚至在另外550次循环后仍保持1239.5 mA h g。电化学测量揭示了高密度FeO点@C层增强的电容行为，通过微分电容图证实，其具有更多用于锂离子嵌入/脱出的额外活性位点，从而导致循环过程中比容量显著增加。重构后的电极还表现出优异的倍率性能和出色的循环稳定性（在1000和2000 mA g的电流密度下分别经过2000次循环后，比容量分别为938.7和815.4 mA h g）。X射线光电子能谱和透射电子显微镜表征表明，即使在大电流密度下，优化后的结构也具有稳定的结构和成分稳定性。这项工作提出了一种通过内应力破碎优化的MOF引导合成高密度FeO点阳极材料的方法，展示了一条设计高效电极材料的可行途径。
