Supporting Information

Potassium cobalt hexacyanoferrate nanocubic assemblies for high-

performance aqueous aluminum ion batteries

Yue Ru, Shasha Zheng, Huaiguo Xue and Huan Pang*

School of Chemistry and Chemical Engineering, Guangling College, Yangzhou University, Yangzhou, 225009, Jiangsu, P. R. China.

E-mail: huanpangchem@hotmail.com; panghuan@yzu.edu.cn

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Contents

Section A. Supplementary Methods

Section B. Supplementary Data

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Section A. Supplementary Methods

Experimental

Materials

All chemicals, Co(NO3)2·6H2O, C6H5Na3O7·2H2O, K3Fe(CN)6, acetylene black, and

polytetrafluoroethylene (PTFE) and isopropanol, were purchased from Shanghai Sinopharm

Chemical Reagent Co. and used without further purification. All aqueous solutions were

freshly prepared with high purity water.

Preparation of CoFe-PBAs

The K2CoFe(CN)6 was synthesized via a one-step hydrothermal method and low-temperature

calcination process. Firstly, the CoFe-PBA precursor was prepared. In a typical preparation, 4

mmol (1.164 g) Co(NO3)2·6H2O and 5.61 mmol (1.65 g) C6H5Na3O7·2H2O were dissolved in

50 mL deionized water to form a homogeneous solution A. At the same time, 2.67 mmol

(0.878 g) K3Fe(CN)6 was dissolved in 50 mL deionized water to form a transparent solution B

as well. The solution B was slowly dropped into the solution A using a pipette and stirred for

5 minutes. Afterwards, the mixed solution was heating in a constant temperature water bath at

25-30 oC for 24 hours to obtain the puce precipitate. The resulting precipitates was collected

by centrifugation and washed with deionized water and ethanol three times respectively and

then dried in vacuum oven at 60 oC for 4 h. At this point, the CoFe-PBA precursor was

synthesized. Then, the as-prepared CoFe-PBA precursor was heated to 100 oC at a rate of 1

oC/min in a tube furnace under nitrogen flow and maintain the temperature at 100 oC for 1h to

form K2CoFe(CN)6. Similar to the calcination method of the K2CoFe(CN)6, other calcined

products (R1, R2 and R3) were heated to 50 oC, 200 oC and 300 oC, respectively.

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Characterization

The morphological features were characterized by field emission scanning electron

microscopy (FESEM, Zeiss-Supra55), high resolution transmission electron microscopy

(HRTEM, Tecnai G2 F30 S-TWIN), and energy dispersive X-ray spectrometry (EDS)

mapping. X-ray diffraction (XRD) patterns were examined on a Bruker D8 Advanced X-ray

Diffractometer (Cu-Kα radiation: λ = 0.15406 nm). The chemical states were measured using

an Axis Ultra X-ray photoelectron spectroscope (XPS, Kratos Analytical Ltd., UK) equipped

with a standard monochromatic Al-Kα source (hv=1486.6 eV). Fourier transform infrared

(FTIR) transmission spectra were obtained on a BRUKER-EQUINOX-55 IR

spectrophotometer. Thermogravimetric measurements were determined via a PerkinElmer

Pyris 1 TGA thermogravimetric analysis (TGA) instrument. Nitrogen adsorption-desorption

measurements were performed on a Gemini VII 2390 analyzer at 77 K using the volumetric

method. The specific surface area was obtained from the N2 adsorption-desorption isotherms

and was calculated by the BET method.

Electrochemical Measurements

Fabrication of working electrodes

Activated materials, the CoFe-PBA samples (K2CoFe(CN)6, R0-R3), acetylene black, and

polytetrafluoroethylene (PTFE) were well mixed to form a mixture with a weight ratio of

80:16:8 in isopropanol. After the isopropanol was evaporated, such mixture was pressed onto

a Titanium mesh (The area=1×1 cm2) under a pressure of 30 MPa as the working electrode.

Electrochemical characterization on working electrodes

Electrochemical measurements were carried out on an electrochemical working station (CHI

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660D, Shanghai Chenhua) in a three-electrode system, in which the CoFe-PBA electrode was

used as the working electrode, the platinum electrode as a counter electrode and the saturated

calomel (SCE) electrode as the reference electrode. The electrolyte was 1.0 M Al(NO3)3

solution. To compare the cation effects on Al insertion The CoFe-PBA electrodes were tested

with cyclic voltammetry and galvanostatic charge-discharge methods. In the galvanostatic

charge/discharge test, the potential ranged from 0 to 1.2 V (vs. SCE). All the electrochemical

measurements were performed at ambient temperature.

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Section B. Supplementary data

Figure S1. SEM images of CoFe-PBA samples for (a, b) R0, (c, d) R1, (e, f) R2 and (g, h) S6

R3.

Figure S2. TGA of the CoFe-PBA precursor (R0) in N2.

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Figure S3. XRD pattern of R0-R3 samples.

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Figure S4. FTIR patterns of the K2CoFe(CN)6 and R0-R3 samples.

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Figure S5. (a) N2 absorption and desorption isotherms. (b) Mesoporous size distributions. (c) Micropore size distributions of the K2CoFe(CN)6.

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Figuure S6. Relationship between peak current densities and potential scanning rates of the K2CoFe(CN)6 and R0-R3 samples as working electrode in Al(NO3)3 aqueous solution.

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Figure S7. EIS measurements of the K2CoFe(CN)6 and R0-R2 samples.

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Figure S8. SEM of the K2CoFe(CN)6 after several electrochemical testments.

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Figure S9. Electrochemical performance of K2CoFe(CN)6 electrode in Al2(SO4)3 and AlCl3

electrolytes: a, c) Typical CV curves in Al2(SO4)3 and AlCl3, b, d) Charge/discharge profiles in Al2(SO4)3 and AlCl3.

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Figure S10. EIS measurements of the K2CoFe(CN)6 in different types of electrolyte.

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