Electronic Supplementary Information (ESI)

Prussian blue nanocubes as cathode materials for

aqueous Na-Zn hybrid batteries

Li-Ping Wang,ab Peng-Fei Wang,ab Tai-Shan Wang,ab Ya-Xia Yin,ab Yu-Guo Guo*ab

and Chun-Ru Wang*ab

a CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, and Beijing

National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese

Academy of Sciences (CAS), Beijing 100190, P.R. China.

b School of Chemistry and Chemical Engineering, University of Chinese Academy of

Sciences, Beijing 100049, P.R. China.

* To whom correspondence should be addressed. E-mail: ygguo@iccas.ac.cn ; crwang@iccas.ac.cn

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Experimental

NaFe-PB synthesis: Typically, 100 mL deionized water including 1.94 g

Na4Fe(CN)6·10H2O and 1 mL hydrochloric acid (37%) solution was firstly heated at

60 ˚C under vigorous stirring. At first, [Fe(CN)6]4- was decomposed to Fe2+ slowly,

after that, Fe2+ was subsequently oxidized to Fe3+ due to its instability in the acidic

atmosphere. Afterwards, Fe2+/Fe3+ reacted with the undecomposed [Fe(CN)6]4- to form

NaFe-PB nanocube nuclei. After maintaining for four hours, the resulting precipitates

were centrifuged and washed with deionized water and ethanol consequently for

several times. Finally, the production was dried in vacuum oven under 80 ˚C

overnight.

LQ-NaFe synthesis: 100 mL deionized water including 1 mM Na4Fe(CN)6·10H2O and

10 mL deionized water including 2 mM Fe(NO3)3·9H2O were mixed under 60 ˚C

under vigorous stirring. The resulting product was centrifuged after four hours, and

washed with deionized water and ethanol consequently for several times. Finally, the

production was dried under 80 ˚C overnight.

Materials characterizations: the morphology and particle size of the obtained samples

were examined by scanning electron microscopy (SEM, JEOL 6701F) operated at 10

kV and transmission electron microscopy (TEM, JEM 2100F) with energy dispersive

spectroscopy (EDS) operated at 200 kV. Powder X-ray diffraction (XRD) patterns

were recorded on a Rigaku D/max-2500 diffractometer with filtered Cu Kα radiation

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(λ = 1.5405 Å). The chemical composition were examined by elemental analysis

(Flash EA 1112) for C, H and N elements and by inductively coupled plasma

spectroscopy (ICP–AES, Shimadzu ICPE-9000) Fe and Na elements. The X-ray

photoelectron spectra (XPS) of the samples were conducted on ESCALab 250Xi

(Thermo Scientific) spectrometer equipped with an Al Kα achromatic X-ray source.

The binding energies of all the elements were calibrated with respect to carbon (284.6

eV) and the XPS peaks were deconvoluted by Avantage software. Raman spectra were

recorded on a DXR Raman Microscope (Thermo Scientific) with a laser wavelength

of 532 nm. Thermogravimetric analysis (TG) conducted on a TG/DTA6300

instrument at heating rate of 2 ˚C min−1 under N2 environment.

Electrochemical measurements: electrochemical characterization of the NaFe-PB

sample was carried out by using a three-electrode cell, in which a piece of Pt and zinc

electrode (-0.76 V vs NHE) were applied as counter and reference electrodes. The

working electrode was prepared by casting 70 wt % active materials, 20 wt % Ketjen

black and 10 wt % polytetrafluoroethylene (PTFE) onto the stainless steel grids. The

electrolyte was aqueous 1 M Na2SO4 solution (pH = 6.5). To couple a full aqueous

battery, the 2032 coin type aqueous hybrid-ion battery was assembled using NaFe-PB

cathode, Zn anode and a porous glass fiber separator ((GF/D) from Whatman). Cyclic

voltammetry (CV) was carried out on a ParSTAT MC electrochemical work station

(Princeton). Galvanostatic tests were carried out in the voltage range 0.9–1.6 V vs

Zn2+/Zn using LAND cycler (Wuhan Kingnuo Electronic Co., China) at 25 ˚C.

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Fig. S1 XPS curve of the as-prepared NaFe-PB.

Fig. S2 SAED pattern of (a) the as-prepared NaFe-PB and (b) LQ-PB.

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Fig. S3 TG curve of the as-prepared NaFe-PB and LQ-NaFe.

Fig. S4 Typical SEM images of cathode (NaFe-PB, ketjen black mixture), (a) (b)

before charge/discharge; (c) (d) after charge/discharge for 1000 cycles.

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Table S1 Elemental contents of NaFe-PB.

Element Weight percentage

N 24.2%

C 20.7%

H 1.64%

Na 4.0%

Fe 34.2%

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Table S2 Comparison of the electrochemical performance of metal-ion aqueous

batteries between this work and the previous reports.

Materials Type of ions Capacity

mA h g-1

Cycling stability Reference

NiO//Zn Zn2+ 155 60%/500 cycles [1]

CuHCF//Zn Zn2+ 53 96.3%/100 cycles [2]

Na0.44MnO2//Ac Na+ 45 100%/1000cycles [3]

Na3V2(PO4)3/

C//Zn

Zn2+, Na+ 86 68%/200 cycles [4]

NiHCF//Zn Zn2+, Na+ 76.2 81%/1000 cycles [5]NaMnO2//

NaTi2(PO4)3

Na+ 55 75%/500cycles [6]

FeFe(CN)6//Zn Zn2+ 120 99%/-- [7]

NaTi2(PO4)3//

Na2NiFe(CN)6

Na+ 65 88%/250 cycles [8]

K0.27MnO2//

NaTi2(PO4)3

Na+ 84.9 83%/100 cycles [9]

N

a0.61Fe1.94(CN)6·□

0.06//Zn

Na+, Zn2+ 73.5 80%/1000 cycles This work

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Reference

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