Supporting Information Available Mesoporous Amorphous FePO4 ...
Supporting Information Available
Mesoporous Amorphous FePO4 Nanospheres as High-performance Cathode Material for Sodium-ion Batteries Yongjin Fang, † Lifen Xiao, * ‡ Jiangfeng Qian, † Xinping Ai, † Hanxi Yang, † and Yuliang Cao *† †
Hubei Key Lab. of Electrochemical Power Sources, College of Chemistry and Molecular
Sciences, Wuhan University, Wuhan 430072, China. ‡
College of Chemistry, Central China Normal University, Wuhan 430079, China.
*CORRESPONDING AUTHOR: E-mail: [email protected]. Phone: +86-027-68754526 and E-mail: [email protected].
Experimental Section Material preparation: All the reagents were purchased from Alfa Aesar and used without further purifying. Mesoporous amorphous FePO4 nanosphere was prepared by a chemically induced precipitation method. Firstly, 0.02 mol of (NH4)2Fe(SO4)2 and NH4H2PO4 were dissolved in 500 mL of
deionized water, respectively. The NH4H2PO4 solution was added
1
slowly to the (NH4)2Fe(SO4)2 solution to form a uniform sol under vigorous stirring. Then 4 mL of 30 wt% H2O2 solution acted as an oxidizer, was added dropwise into the colloid solution. The solution was stirred for another 2 hrs to produce a light yellow amorphous FePO4·3H2O precipitation. The FePO4·3H2O precursor was subsequently dehydrated at 400 °C for 24 hrs in air to form an amorphous FePO4. Finally, the amorphous FePO4 was ball-milled with carbon black (Ketjen Black) in a weight ratio of 7:2 for 2 hrs to obtain a FePO4/C nanocomposite. Characterization: X-ray powder diffraction patterns were obtained by using a Shimadzu XRD-6000 diffractometer with Cu Kα. The diffraction data were recorded in the 2θ range of 10-80° with a scan rate of 2° min-1. The morphologies of the materials were observed by using SEM (Sirion, 2000, FEI) and TEM (JEM-2010FEF). The energy-dispersive spectroscopy (EDS) was recorded by using an SUTW-SAPPHIRE detector attached to the TEM. Thermogravimetric measurement (TG) was conducted on a TGA Q500 thermogravimetric analyzer (TA Intrusment, U.S.A.) in air at a heating rate of 10 °C min-1 from room temperature to 550 °C. N2 adsorption/desorption isotherms were measured at liquid nitrogen temperature using ASAP 2020. Micro-Raman spectra were obtained from an InVia Raman microspectrometer (Renishaw, UK) with 514.5 nm radiation at a laser power of 0.4 mW in the range of 500-2000 cm-1. Electrochemical measurements: Electrochemical characterization was carried out using 2016 coin cells. The FePO4/C cathodes were prepared by applying the paste containing 90 wt% of FePO4/C and 10 wt% of poly(vinyl difluoride) (PVdF) onto a Al foil. For comparison, the bare FePO4 cathode was made up of 70 wt% FePO4, 20 wt% ketjen black and 10 wt% poly(vinyl difluoride) (PVdF). The average mass loading was about 2 mg cm-2. The electrolyte was 1.0 mol L–1 NaPF6 dissolved in ethylene carbonate/diethyl carbonate (EC/DEC, 1:1 by vol.) solution. The Na thin disks were used as anodes. All the cells were assembled in a glove box with
2
water/oxygen content lower than 1 ppm and tested at room temperature. The galvanostatic discharging–charging tests were conducted on a LAND cycler (Wuhan Kingnuo Electronic Co., China). Cyclic voltammetric measurements were performed at a scan rate of 0.1 mV s−1 on a CHI 660a electrochemical workstation (ChenHua Instruments Co., China).
Figure S1 EDS spectrum of the FePO4 nanospheres. The inset indicates the element content of the mapping area. The EDS mapping analysis shows that the nanoshpheres are composed of Fe, P, O, and the P/Fe ratio is 1.16, indicating that the nanospheres are amorphous FePO4. The Cu (8.05 keV) signal arises from the Cu carrier used for TEM measurement.
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Figure S2 (a) and (b) TEM images of the FePO4 nanospheres. The nanospheres are about 80-100 nm and interspersed with a large number of mesopores; c) TEM image of the FePO4/C composite.
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Figure S3 N2 adsorption/desorption isotherms of the FePO4 nanospheres. A type IV isotherm is observed, characterizing a mesoporous structure of the FePO4 nanospheres.
Figure S4 Raman spectra of the FePO4 nanospheres and the FePO4/C composite.
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Figure S5 A typical Tyndall effect when light goes through the ferrous phosphate colloidal solution.
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Figure S6 Electrochemical characterization of the FePO4 cathode (voltage window 1.5–4.0 V): (a) discharging/charging curves of the FePO4 cathode; (b) cycling performance of the FePO4 cathode at 20 mA g-1; (c) Rate capability of FePO4 cathode. The counter electrode was a Na disk and the electrolyte was 1.0 mol L−1 NaPF6 dissolved in a mixed EC/DEC solution (EC: DEC=1:1 by vol.).
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Figure S7 The XRD patterns of the FePO4/C cathodes at full discharging and charging states. No crystalline peak appears throughout the whole discharging/charging processes expect for the Al current collector
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Mesoporous Amorphous FePO4 Nanospheres as High-performance Cathode Material for Sodium-ion Batteries Yongjin Fang, † Lifen Xiao, * ‡ Jiangfeng Qian, † Xinping Ai, † Hanxi Yang, † and Yuliang Cao *† †
Hubei Key Lab. of Electrochemical Power Sources, College of Chemistry and Molecular
Sciences, Wuhan University, Wuhan 430072, China. ‡
College of Chemistry, Central China Normal University, Wuhan 430079, China.
*CORRESPONDING AUTHOR: E-mail: [email protected]. Phone: +86-027-68754526 and E-mail: [email protected].
Experimental Section Material preparation: All the reagents were purchased from Alfa Aesar and used without further purifying. Mesoporous amorphous FePO4 nanosphere was prepared by a chemically induced precipitation method. Firstly, 0.02 mol of (NH4)2Fe(SO4)2 and NH4H2PO4 were dissolved in 500 mL of
deionized water, respectively. The NH4H2PO4 solution was added
1
slowly to the (NH4)2Fe(SO4)2 solution to form a uniform sol under vigorous stirring. Then 4 mL of 30 wt% H2O2 solution acted as an oxidizer, was added dropwise into the colloid solution. The solution was stirred for another 2 hrs to produce a light yellow amorphous FePO4·3H2O precipitation. The FePO4·3H2O precursor was subsequently dehydrated at 400 °C for 24 hrs in air to form an amorphous FePO4. Finally, the amorphous FePO4 was ball-milled with carbon black (Ketjen Black) in a weight ratio of 7:2 for 2 hrs to obtain a FePO4/C nanocomposite. Characterization: X-ray powder diffraction patterns were obtained by using a Shimadzu XRD-6000 diffractometer with Cu Kα. The diffraction data were recorded in the 2θ range of 10-80° with a scan rate of 2° min-1. The morphologies of the materials were observed by using SEM (Sirion, 2000, FEI) and TEM (JEM-2010FEF). The energy-dispersive spectroscopy (EDS) was recorded by using an SUTW-SAPPHIRE detector attached to the TEM. Thermogravimetric measurement (TG) was conducted on a TGA Q500 thermogravimetric analyzer (TA Intrusment, U.S.A.) in air at a heating rate of 10 °C min-1 from room temperature to 550 °C. N2 adsorption/desorption isotherms were measured at liquid nitrogen temperature using ASAP 2020. Micro-Raman spectra were obtained from an InVia Raman microspectrometer (Renishaw, UK) with 514.5 nm radiation at a laser power of 0.4 mW in the range of 500-2000 cm-1. Electrochemical measurements: Electrochemical characterization was carried out using 2016 coin cells. The FePO4/C cathodes were prepared by applying the paste containing 90 wt% of FePO4/C and 10 wt% of poly(vinyl difluoride) (PVdF) onto a Al foil. For comparison, the bare FePO4 cathode was made up of 70 wt% FePO4, 20 wt% ketjen black and 10 wt% poly(vinyl difluoride) (PVdF). The average mass loading was about 2 mg cm-2. The electrolyte was 1.0 mol L–1 NaPF6 dissolved in ethylene carbonate/diethyl carbonate (EC/DEC, 1:1 by vol.) solution. The Na thin disks were used as anodes. All the cells were assembled in a glove box with
2
water/oxygen content lower than 1 ppm and tested at room temperature. The galvanostatic discharging–charging tests were conducted on a LAND cycler (Wuhan Kingnuo Electronic Co., China). Cyclic voltammetric measurements were performed at a scan rate of 0.1 mV s−1 on a CHI 660a electrochemical workstation (ChenHua Instruments Co., China).
Figure S1 EDS spectrum of the FePO4 nanospheres. The inset indicates the element content of the mapping area. The EDS mapping analysis shows that the nanoshpheres are composed of Fe, P, O, and the P/Fe ratio is 1.16, indicating that the nanospheres are amorphous FePO4. The Cu (8.05 keV) signal arises from the Cu carrier used for TEM measurement.
3
Figure S2 (a) and (b) TEM images of the FePO4 nanospheres. The nanospheres are about 80-100 nm and interspersed with a large number of mesopores; c) TEM image of the FePO4/C composite.
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Figure S3 N2 adsorption/desorption isotherms of the FePO4 nanospheres. A type IV isotherm is observed, characterizing a mesoporous structure of the FePO4 nanospheres.
Figure S4 Raman spectra of the FePO4 nanospheres and the FePO4/C composite.
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Figure S5 A typical Tyndall effect when light goes through the ferrous phosphate colloidal solution.
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Figure S6 Electrochemical characterization of the FePO4 cathode (voltage window 1.5–4.0 V): (a) discharging/charging curves of the FePO4 cathode; (b) cycling performance of the FePO4 cathode at 20 mA g-1; (c) Rate capability of FePO4 cathode. The counter electrode was a Na disk and the electrolyte was 1.0 mol L−1 NaPF6 dissolved in a mixed EC/DEC solution (EC: DEC=1:1 by vol.).
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Figure S7 The XRD patterns of the FePO4/C cathodes at full discharging and charging states. No crystalline peak appears throughout the whole discharging/charging processes expect for the Al current collector
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