Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA.
Nat Nanotechnol. 2015 Nov;10(11):980-5. doi: 10.1038/nnano.2015.194. Epub 2015 Sep 7.
Sodium-ion batteries have recently attracted significant attention as an alternative to lithium-ion batteries because sodium sources do not present the geopolitical issues that lithium sources might. Although recent reports on cathode materials for sodium-ion batteries have demonstrated performances comparable to their lithium-ion counterparts, the major scientific challenge for a competitive sodium-ion battery technology is to develop viable anode materials. Here we show that a hybrid material made out of a few phosphorene layers sandwiched between graphene layers shows a specific capacity of 2,440 mA h g(-1) (calculated using the mass of phosphorus only) at a current density of 0.05 A g(-1) and an 83% capacity retention after 100 cycles while operating between 0 and 1.5 V. Using in situ transmission electron microscopy and ex situ X-ray diffraction techniques, we explain the large capacity of our anode through a dual mechanism of intercalation of sodium ions along the x axis of the phosphorene layers followed by the formation of a Na3P alloy. The presence of graphene layers in the hybrid material works as a mechanical backbone and an electrical highway, ensuring that a suitable elastic buffer space accommodates the anisotropic expansion of phosphorene layers along the y and z axial directions for stable cycling operation.
钠离子电池作为锂离子电池的替代品，近年来受到了极大的关注，因为钠资源不会像锂资源那样存在地缘政治问题。尽管最近关于钠离子电池正极材料的报道已经展示出与锂离子电池相当的性能，但开发有竞争力的钠离子电池技术的主要科学挑战是开发可行的负极材料。在这里，我们展示了由几层磷烯层夹在石墨烯层之间组成的混合材料，在电流密度为 0.05 A/g 时，具有 2440 mA h/g（仅使用磷的质量计算）的比容量，在 0 到 1.5 V 之间循环 100 次后，容量保持率为 83%。通过原位透射电子显微镜和非原位 X 射线衍射技术，我们通过磷烯层沿 x 轴插层钠离子的双重机制以及 Na3P 合金的形成来解释我们阳极的高容量。在混合材料中加入石墨烯层作为机械骨架和电子高速公路，确保了合适的弹性缓冲空间能够容纳磷烯层沿 y 和 z 轴向的各向异性膨胀，从而实现稳定的循环运行。
