Supporting Information Excellent cycling stability and superior rate capability of graphene- amorphous FePO 4 porous nanowire hybrid as cathode material for sodium ion batteries Gaoliang Yang a , Bing Ding a , Jie Wang a , Ping Nie a , Hui Dou a , and Xiaogang Zhang* a Jiangsu Key Laboratory of Materials and Technology for Energy Conversion, College of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, P. R. China. E-mail: azhangxg@nuaa.edu.cn Experimental section Material synthesis Preparation of graphene-amorphous FePO 4 porous nanowire hybrid. Graphene-amorphous FePO 4 porous nanowire hybrid were synthesized by a hydrothermal approach which has been reported by Cai et al. previously [S1] , followed by stirring with hydrazine hydrate under 90 o C. In a typical synthesis, GO solution was firstly synthesized by oxidizing graphite powder in a strong acidic medium, according to a modified Hummer's method. And then, (NH 4 ) 2 Fe(SO 4 ) 2 ·6H 2 O (0.1176 g), H 3 PO 4 (123 μL), urea (3.6 g), and SDS (0.3 g) were dissolved in the homogeneous GO suspension (60 mL, 0.25 mg mL –1 ). The mixture was vigorously stirred for approximately 10 min, transferred into an autoclave, and heated to 80 °C for 12 h. After naturally cooling to ambient temperature, the resulting products were collected by centrifugation, washed sequentially with distilled water and ethanol at least three times, and then dried at 100 °C for 12 h. The obtained products were then mixed with 5 mL hydrazine hydrate in a sealed bottle and stirred for 24 h under 90 o C. After cooling down naturally, the products were obtained by centrifugation and then dried at 100 o C for 12 h. Materials characterization Electronic Supplementary Material (ESI) for Nanoscale. This journal is © The Royal Society of Chemistry 2016