SUPPORTING INFORMATION

High-rate performance electrospun Na0.44MnO2

nanofibers as cathode material for sodium-ion batteriesBi Fua, b, Xuan Zhou,b,*and Yaping Wanga,*

a School of Science, and MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of Chinab Department of Electrical and Computer Engineering, Kettering University, Flint, MI-48504, USA

1. Fiber diameter distribution

Fig. S1: Fiber diameter distribution of the (a) as-spun precursor NFs, and the calcined

Na0.44MnO2 NFs at different temperatures: (b) 400 °C, (c) 500 °C, (d) 600 °C, and (e)

800 °C.

2. TG-DTA analysis of the electrospun precursor NFs

TG curve in Fig. S2 indicates that the precursor NFs undergo three primary weight

loss steps with the increase of temperature. The primary weight loss of 10 % in the

range of 0 °C to 280 °C is believed resulting from the volatilization of DI water and

CH3COOH. Correspondingly, an endothermic peak is observed in the DTA curve

around 80 °C. The biggest weight loss occurred at 280 °C to 580 °C, which is due to

the decomposition of the PVA. There is no obvious weight loss and heat flow at the

580 °C to 900 °C scope, which indicates the thorough decomposition of PVA as well

as the formation of NaxMnO2.

Fig. S2: TG and DTA curves of the as-spun precursor NFs.

3. SEM image of the Na0.44MnO2 NFs annealed at 900 °C for 1 h.

Fig. S3: SEM image of the Na0.44MnO2 NFs annealed at 900 °C for 1 h.

4. XRD pattern of the NaxMnO2 specimen with different x value at different

temperature.

The XRD pattern in Fig. S4 shows the as-spun NaxMnO2 (x = 0.45, 0.46, 0.47,

0.48, 0.49, 0.50) precursor NFs annealed at 600 °C for 1 h. It reveals that some

impurities Mn-based oxides such as Mn3O4, MnO2, and Mn2O3 appeared in the

specimens when x = 0.45 and 0.46. The Na0.7MnO2 phase dominates the x = 0.49 and

0.50 specimen. The x = 0.47 and 0.48 is the correct component of Na0.44MnO2 phase.

The XRD pattern of the 800 °C annealed NaxMnO2 (x = 0.45, 0.46, 0.47, 0.48, 0.49

and 0.50) precursor NFs in Fig. S5 confirmed that the x = 0.49 specimen corresponds

to the Na0.44MnO2 phase structure. The impurity of the Mn2O3 increased with

increasing of x. The Na0.77MnO2 phase appears in the annealed Na0.53MnO2 precursor

NFs specimen. Consequently, the Na0.44MnO2 NRs were generated by annealing the

Na0.49MnO2 precursor NFs at 800 °C for 1 h.

Fig. S4: XRD pattern of the Na0.44MnO2 precursor solution annealed at different

temperature for 1 h.

Fig. S5: XRD pattern of the NaxMnO2 (x = 0.45, 0.46, 0.47, 0.48, 0.49, and 0.50)

precursor solution annealed at 600 °C for 1 h.

Fig. S6: XRD pattern of the NaxMnO2 (x = 0.48, 0.49, 0.50, 0.51, 0.52, and 0.53)

precursor solution annealed at 800 °C for 1 h.

5. Galvanostatic charge/discharge profiles of Na0.44MnO2 NFs

Fig. S7: Galvanostatic charge/ discharge profiles of Na0.44MnO2 NFs (a) cycling at

different cycles, and (b) cycling at different rates.

Fig. S8: Relationship between Zreal and -1/2 at low frequency.

Fig. S9: Differentiate discharge curve and the corresponding incremental capacity

curve of Na0.44MnO2 (a) NF and (b) NR.