School of Materials Science and Engineering and Tianjin Key Laboratory of Composites and Functional Materials, Tianjin University, Tianjin 300072, People's Republic of China.
ACS Nano. 2013 May 28;7(5):4459-69. doi: 10.1021/nn401059h. Epub 2013 Apr 30.
A facile and scalable in situ synthesis strategy is developed to fabricate carbon-encapsulated Fe3O4 nanoparticles homogeneously embedded in two-dimensional (2D) porous graphitic carbon nanosheets (Fe3O4@C@PGC nanosheets) as a durable high-rate lithium ion battery anode material. With assistance of the surface of NaCl particles, 2D Fe@C@PGC nanosheets can be in situ synthesized by using the Fe(NO3)3·9H2O and C6H12O6 as the metal and carbon precursor, respectively. After annealing under air, the Fe@C@PGC nanosheets can be converted to Fe3O4@C@PGC nanosheets, in which Fe3O4 nanoparticles (∼18.2 nm) coated with conformal and thin onion-like carbon shells are homogeneously embedded in 2D high-conducting carbon nanosheets with a thickness of less than 30 nm. In the constructed architecture, the thin carbon shells can avoid the direct exposure of encapsulated Fe3O4 to the electrolyte and preserve the structural and interfacial stabilization of Fe3O4 nanoparticles. Meanwhile, the flexible and conductive PGC nanosheets can accommodate the mechanical stress induced by the volume change of embedded Fe3O4@C nanoparticles as well as inhibit the aggregation of Fe3O4 nanoparticles and thus maintain the structural and electrical integrity of the Fe3O4@C@PGC electrode during the lithiation/delithiation processes. As a result, this Fe3O4@C@PGC electrode exhibits superhigh rate capability (858, 587, and 311 mAh/g at 5, 10, and 20 C, respectively, 1 C = 1 A/g) and extremely excellent cycling performance at high rates (only 3.47% capacity loss after 350 cycles at a high rate of 10 C), which is the best one ever reported for an Fe3O4-based electrode including various nanostructured Fe3O4 anode materials, composite electrodes, etc.
一种简便且可扩展的原位合成策略被开发用于制备均匀嵌入二维（2D）多孔石墨化碳纳米片（Fe3O4@C@PGC 纳米片）中的碳包覆 Fe3O4 纳米粒子，作为一种耐用的高倍率锂离子电池阳极材料。在 NaCl 颗粒的表面作用下，分别使用 Fe(NO3)3·9H2O 和 C6H12O6 作为金属和碳前体，原位合成 2D Fe@C@PGC 纳米片。在空气下退火后，Fe@C@PGC 纳米片可以转化为 Fe3O4@C@PGC 纳米片，其中均匀嵌入厚度小于 30nm 的 2D 高导碳纳米片中的 Fe3O4 纳米颗粒（约 18.2nm）被薄的洋葱状碳壳包覆。在构建的结构中，薄的碳壳可以避免包裹的 Fe3O4 纳米颗粒直接暴露于电解质中，并保持 Fe3O4 纳米颗粒的结构和界面稳定性。同时，柔性和导电的 PGC 纳米片可以容纳嵌入 Fe3O4@C 纳米颗粒体积变化引起的机械应力，并抑制 Fe3O4 纳米颗粒的聚集，从而在锂化/脱锂过程中保持 Fe3O4@C@PGC 电极的结构和电完整性。结果，该 Fe3O4@C@PGC 电极表现出超高倍率性能（在 5、10 和 20 C 时分别为 858、587 和 311 mAh/g，1 C = 1 A/g）和在高倍率下的优异循环性能（在 10 C 的高倍率下循环 350 次后仅损失 3.47%的容量），这是迄今为止报道的基于 Fe3O4 的电极中最好的，包括各种纳米结构的 Fe3O4 阳极材料、复合电极等。
