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.
Nature Nanotechnology (2015) doi:10.1038/nnano.2015.194
Received 30 October 2014 Accepted 27 July 2015 Published online 07 September 2015
http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2015.194.html
http://mp.weixin.qq.com/s?__biz=MzA5NzIyNjEzNQ==&mid=209705502&idx=3&sn=9d80f549bc88a1ac1cad3394ef656c99&scene=0#rd
