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Construction of Amorphous FePO4 Nanosheets with Enhanced Sodium Storage Properties Zhuangzhuang Zhang, Yu Han, Jiamin Xu, Jinghan Ma, Xiaosi Zhou,* and Jianchun Bao Jiangsu Key Laboratory of New Power Batteries, Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China
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ABSTRACT: Two-dimensional (2D) nanomaterials have drawn enormous attention as anode materials for sodiumion batteries. However, the synthesis of 2D cathode materials for advanced sodium-ion batteries remains a big challenge. Herein, amorphous FePO4 nanosheets are successfully synthesized through a simple template method. The assynthesized amorphous FePO4 nanosheets possess a mesoporous structure. Electrochemical measurements reveal that the amorphous FePO4 nanosheets exhibit a large initial discharge capacity of 126.4 mAh g−1 at a current density of 20 mA g−1, superior cycling performance (89.8% capacity retention over 100 cycles), and high rate capability (42.1 mAh g−1 at 1000 mA g−1). These results indicate that the amorphous FePO4 nanosheets can serve as a promising cathode material for sodium-ion batteries. KEYWORDS: FePO4, amorphous nanosheets, mesoporous structure, sodium storage, cathode
1. INTRODUCTION While lithium-ion batteries (LIBs) still dominate the power sources for electrical vehicles and stationary energy storage systems, sodium-ion batteries (SIBs) have recently attracted ever-increasing attention for the application of large-scale energy storage benefiting from their outstanding merits including environmental benignity, low cost, and wide availability of Na.1−7 Compared with lithium ions, sodium ions encompass larger ionic radius and can easily destroy the electrode structure during the repeated sodiation/desodiation processes.8−11 Therefore, it is urgent to search for reliable Na+ host materials for the application of SIB technology.12,13 With unremitting efforts of researchers, abundant electrode materials have been investigated for SIBs, such as hard carbons,14−18 transition metal oxides/sulfides,19−26 phosphates,27,28 Prussian blue-based compounds,29,30 and alloy-type materials.31−37 Nevertheless, from the economic and environmental perspectives some earth-rare elements, involving V, Co, and Ni, are unsuitable for implementation in large-scale energy storage. In contrast, the earth-abundant element Fe is inexpensive and ecofriendly. Therefore, Fe-based compounds have recently drawn a great deal of interest for being exploited as low-cost and green cathode materials for SIBs. Among diverse Fe-containing cathode materials, FePO4based compounds are mostly surveyed, including NaFePO4,38,39 Na2FeP2O7,40,41 and FePO4.42,43 Similar to LiFePO4, NaFePO4 was investigated early as an appealing cathode candidate for SIBs.38,44 In fact, it is reported that NaFePO4 owns two phases of maricite and olivine.45,46 The maricite NaFePO4 is a thermally stable phase and can be readily synthesized by conventional solid-state fabrication route; however, it is electrochemically inactive owing to the absence © XXXX American Chemical Society
of available cationic channel. By contrast, olivine NaFePO4 presents outstanding electrochemical activity for sodium storage, yet it only can be achieved by the cation exchange strategy from LiFePO4.47 Na2FeP2O7 has a triclinic structure and possesses huge sodium-ion transportation channels but only exhibits a poor reversible capacity of 82 mAh g−1.40 Up to now, the sodium storage performances of crystalline iron phosphates have been less desirable because the crystal frameworks either cannot offer an effective pathway for Na+ diffusion or are deficient of sufficient sodium storage sites.48 To circumvent these issues, fabrication of amorphous structure appears to be an effective measure because the structural hindrance to the sodium-ion uptake/release reaction will be significantly diminished in the amorphous network. Recently, several reports have demonstrated that nanoscale amorphous FePO4 is more electroactive for sodium storage at room temperature.49,50 Nevertheless, the sodium storage properties, especially the cycling performance, of amorphous FePO4 are still undesirable and need to be further enhanced. On the other hand, FePO4 nanoparticles are prone to agglomeration upon sodium-ion uptake/release, which severely restricts their practical applications. In comparison with ordinary nanoparticles, sheet-like nanostructures consisting of nanoscale primary building blocks could not only mitigate the problem of irregular agglomeration but also effectively shorten the transportation distance for both electrons and Na+ ions in FePO4 matrix and offer a high electrode/electrolyte contact area, which are beneficial to boost the rate performance and Received: June 25, 2018 Accepted: July 24, 2018 Published: July 24, 2018 A
DOI: 10.1021/acsaem.8b01027 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX
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ACS Applied Energy Materials
Figure 1. Schematic representation of the fabrication process for the mesoporous amorphous FePO4 nanosheets.
Figure 2. (a) XRD patterns and (b) Raman spectra of the GO@FePO4·3H2O nanosheets and the amorphous FePO4 nanosheets.
cycling stability.51−53 However, until now, the fabrication of sheet-like structured amorphous FePO4, especially with nanometer size, seems unreported. Herein, we demonstrate the successful synthesis of mesoporous amorphous FePO4 nanosheets by a facile template method. When evaluated as a cathode material for SIBs, these amorphous FePO4 nanosheets show improved electrochemical properties with a high discharge capacity of 126.4 mAh g−1 at 20 mA g−1 and excellent cycling performance (89.8% capacity retention over 100 cycles) as well as superior rate capability (42.1 mAh g−1 at 1 A g−1).
electron microscopy (TEM; JEOL JEM-2100F). The composition of the samples was characterized by energy-dispersive X-ray spectroscopy (EDX) linked to the TEM. High-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image and elemental distribution images were acquired on the TEM equipped with a Thermo Fisher Scientific energy-dispersive X-ray spectrometer. Nitrogen sorption measurements were carried out on an ASAP 2050 surface-area and pore-size analyzer. Fourier transform infrared spectroscopy (FT-IR) spectra were acquired using a Thermo Nicolet Nexus 670 FT-IR spectrometer. X-ray photoelectron spectroscopy (XPS) spectra were collected on an ESCALab250Xi electron spectrometer from VG Scientific equipped with 300 W Al Kα radiation. Electrochemical Characterization. Electrochemical measurements were carried out using CR2032 coin cells. The working electrodes were made by spreading the mixed slurry of active material (FePO4 nanosheets or FePO4 microparticles), Super-P carbon black, and poly(vinyl difluoride) (PVDF) in N-methylpyrrolidone with a mass ratio of 6:3:1 onto aluminum foil and then dried at 80 °C under vacuum overnight. The loading densities of cathode films were controlled at ∼1.0 mg cm−2. Separators of grade GF/D from Whatman and counter electrodes of sodium thin sheets as well as an electrolyte of 1 M NaClO4 in a EC/DEC/FEC solution (1:1:0.05 volume ratio) were employed. Galvanostatic charge and discharge measurements were performed on a Land CT2001A multichannel battery testing system in the fixed voltage range between 1.5 and 4.0 V (vs Na+/Na) at different current rates. Cyclic voltammetry (CV) curves and electrochemical impedance spectroscopy (EIS) spectra were collected on a PARSTAT 4000 electrochemical workstation. CV was performed at a scan rate of 0.1 mV s−1, and EIS was obtained by using a sine wave with an amplitude of 10.0 mV between 105 and 0.1 Hz.
2. EXPERIMENTAL SECTION Preparation of GO@FePO4·3H2O Nanosheets. Typically, 62.1 mg of NH4H2PO4 was first dissolved in 100 mL of water. Then 8 mL of graphene oxide (GO) aqueous dispersion (10 mg mL−1) was added into the NH4H2PO4 solution under ultrasonication. Thereafter, 196.1 mg of (NH4)2Fe(SO4)2·6H2O and 0.2 mL of H2O2 solution (30%) were dissolved in the suspension in turn via vigorous stirring. The resulting mixture was aged at ambient temperature for 12 h without stirring. The resultant product of GO@FePO4·3H2O nanosheets were harvested and washed several times with water and finally freeze-dried for 36 h. Preparation of Amorphous FePO4 Nanosheets. The assynthesized GO@FePO4·3H2O nanosheets were calcinated at 400 °C for 24 h in air with a temperature ramp of 1 °C min−1 to achieve the product of amorphous FePO4 nanosheets. For comparison, FePO4 microparticles were bought from Sinopharm Chemical Reagent Co. Ltd. and utilized directly without any purification. Materials Characterization. The thickness measurement of GO nanosheets using atomic force microscopy (AFM) was analyzed using a Digital Instruments NanoScope IIIa atomic force microscope via tapping mode. Structural analysis using X-ray diffraction (XRD) was determined on a Rigaku SmartLab diffractometer equipped with Cu Kα radiation. Raman spectra were recorded on a Labram HR800 apparatus using a laser wavelength of 514 nm. Thermogravimetric analysis (TGA) was performed on a NETZSCH STA 449 F3 instrument under a flowing air environment. The morphology and structure of the samples were confirmed by field-emission scanning electron microscopy (FE-SEM; JEOL JSM-7600F) and transmission
3. RESULTS AND DISCUSSION The synthetic strategy of amorphous FePO4 nanosheets is illustrated in Figure 1. First of all, uniform graphene oxide (GO) nanosheets adopted as the removable templates are covered with a conformal layer of Fe3(PO4)2·8H2O by a coprecipitation method to achieve GO@Fe3(PO4)2·8H2O core@ shell nanosheets due to the electrostatic force between the Fe2+ ions and the oxygen-containing functional groups on both B
DOI: 10.1021/acsaem.8b01027 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX
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Figure 3. Morphological analysis of the GO@FePO4·3H2O nanosheets: (a−c) SEM images, (d, e) TEM images, and (f) high-magnification TEM image.
Figure 4. Morphological analysis and elemental mapping images of the mesoporous amorphous FePO4 nanosheets: (a, b) SEM images, (c) TEM image, (d) STEM image, and (e−g) corresponding elemental distribution images (Fe, P, and O).
sides of GO (step I). Then, the GO@Fe3(PO4)2·8H2O core@ shell nanosheets are oxidized to GO@FePO4·3H2O core@ shell nanosheets in H2O2 aqueous solution (step II). Finally, the GO cores and three molecules of crystal water can be completely eliminated during the annealing treatment in air to produce amorphous FePO4 nanosheets with rich mesopores (step III). Uniform GO nanosheets prepared by a modified Hummers’ method are employed as the templates.54 AFM image shows that these GO nanosheets are relatively uniform with an average size of about 1−3 μm and a mean height of about 1.1 nm (Figure S1). XPS measurement verifies the formation of GO (Figure S2). Uniform FePO4·3H2O shells are obtained after a co-precipitation reaction and subsequent H 2O 2 oxidation. The amorphous structure of the as-prepared GO@ FePO4·3H2O core@shell nanosheets is corroborated by XRD (Figure 2a). The broad peak observed at 22.5° may be owing to the low ordering introduced by the GO template. Panels a−f of Figure 3 display typical SEM and TEM images of the as-
synthesized GO@FePO4·3H2O core@shell structures. The core@shell structure is affirmed by the high-magnification SEM image (Figure 3c), from which it is obvious that thin FePO4·3H2O layers have been grown on the whole surface of GO cores and the thickness of these GO@FePO4·3H2O core@shell nanosheets significantly increases to around 50 nm. The FePO4·3H2O shells are relatively even and thin (thickness of about 24.5 nm). Panels d−f of Figure 3 present the TEM images of a single GO@FePO4·3H2O core@shell nanosheet, demonstrating the sheet-like shape with a mesoporous structure (Figure S3). The increased roughness of these nanosheets in comparison with the original GO nanosheets (Figure S4) further reveals the generation of FePO4·3H2O shells on the core nanosheets. After calcination treatment, the nanosheet structure is wellpreserved without obvious change in morphology (Figure 4). The GO template is totally removed by air oxidation and the FePO4·3H2O overlayer is completely transformed into FePO4 based on FT-IR, TGA, and EDX analysis (Figures S5−S7),55 C
DOI: 10.1021/acsaem.8b01027 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX
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Figure 5. XPS spectrum of the amorphous FePO4 nanosheets: (a) full spectrum and (b−d) high-resolution Fe 2p, P 2p, and O 1s spectra.
Figure 6. Electrochemical characterization of the amorphous FePO4 nanosheets as a cathode material in SIBs: (a) CV curve obtained at 0.1 mV s−1 between 1.5 and 4.0 V, (b, c) galvanostatic charge and discharge profiles conducted at 20 mA g−1 and the relevant cycling stability, and (d) rate performance.
(Figure 4b). The geometrical and mesoporous structure of the as-synthesized FePO4 nanosheets is further unveiled by TEM characterization. Figure 4c shows that the mesoporous structure can be clearly seen in sharp contrast between the FePO4 nanoparticles and mesopores, which are primarily generated by the release of plenty of CO and CO2 during the calcination process. The HAADF-STEM image and corresponding elemental distribution images reveal the uniform allocation of Fe, P, and O elements within the nanosheet (Figure 4d−g). On account of the sheet-like and mesoporous structure,58,59 the as-obtained amorphous FePO4 nanosheets possess a relatively high Brunauer−Emmett−Teller (BET)
to create FePO4 nanosheets. As illustrated by the XRD pattern (Figure 2a), the amorphous structure is preserved in the resulting FePO4 nanosheets. Compared with the Raman spectrum of GO@FePO4·3H2O nanosheets, the appearance of discernible PO43− peaks and the disappearance of D and G bands of GO in the Raman spectra of amorphous FePO4 nanosheets further confirm the successful removal of three molecules of crystal water and GO template from the asformed amorphous FePO4 nanosheets (Figure 2b).56,57 As displayed in the SEM image in Figure 4a, the nanosheet architecture is maintained with a mean size of around 1−3 μm. A close observation of FePO4 nanosheets reveals a rough surface with a thickness determined to be approximately 45 nm D
DOI: 10.1021/acsaem.8b01027 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX
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ACS Applied Energy Materials surface area of 81.9 m2 g−1 (N2 sorption isotherms are shown in Figure S8). The surface elemental composition and chemical status were investigated by XPS in detail. As demonstrated Figure 5a, the XPS survey scan spectra, displays the existence of Fe, P, and O elements ascribed to the material composition of FePO4 nanosheets, while C and N elements are originated from the carbon baseline of the instrument itself and the precursor of NH4H2PO4, respectively. In addition, two peaks for Fe 2p are readily seen at binding energies of 725.81 and 712.36 eV, which can be ascribed to Fe 2p 1/2 and Fe 2p 3/2 , respectively.60,61 There is a large energy gap of 13.45 eV between Fe 2p1/2 and 2p3/2 (Figure 5b), which is inherent to FePO4. Panels c and d of Figure 5 show the prominent peaks at 133.70 and 531.38 eV, corresponding to the representative P 2p and O 1s XPS spectra of the PO43− group, respectively.55 The XPS analysis further verifies the structure of FePO4. Therefore, the XRD, FT-IR, TGA, EDX, and XPS measurements fully corroborate that the FePO4 nanosheets are successfully fabricated. To disclose the merits of these FePO4 nanosheets, we investigated their electrochemical sodium storage performance as a cathode material in SIBs. The CV curve (Figure 6a) is in good agreement with previously reported results.42 The CV profile demonstrates a pair of current peaks located respectively at 2.64 and 2.08 V (Figure 6a), which are associated with the redox of Fe(III)/Fe(II). The wide redox peaks indicate successive single-phase redox reactions,62 which is unlike that of the olivine FePO4 featured by a biphasic transformation during Li+-/Na+-ions insertion and extraction processes.38,63 Figure 6b illustrates typical discharge−charge voltage curves of amorphous FePO4 nanosheets at 20 mA g−1 between 1.5 and 4.0 V. In accord with the CV results, the initial discharge profile shows a well-defined slope, which accords well with other nanosized amorphous FePO4 electrodes that have been previously reported.42,49,50 The first discharge process brings about a relatively high initial capacity of 126.4 mAh g−1, which remarkably exceeds the specific capacity of FePO4 nanoparticles reported before.42 This is probably due to the amorphous nanosheets and mesoporous structure, which offers more surface active sites for sodium storage and some irreversible side reactions on nanosized amorphous FePO4. A slightly poorer capacity of 116.6 mAh g−1 is obtained in the ensuing charge process, resulting in an irreversible capacity loss of 7.8%. The small irreversible capacity loss during the initial cycle is related to the irreversible change of amorphous structure between 1.7 and 1.5 V for a deep sodium uptake.64 The huge volume strain formed during the sodium ions insertion leads to the trapping of Na+ ions inside the structure.65 After the first cycle, the specific capacity of the FePO4 nanosheets electrode is gradually stabilized. All the following cycles display an almost overlapped slope curve of the voltage−capacity relationship during both the sodiation and desodiation processes (Figure 6b). A discharge capacity of 120.2 mAh g−1 is exhibited in the second cycle, followed by a charge capacity of 114.9 mAh g−1, corresponding to a high Coloumbic efficiency (CE) of around 96%. The reversible capacity is retained at 113.5 mAh g−1 after 100 cycles at 20 mA g−1 (Figure 6c), which is superior to most of the reported results from FePO4 (Table S1). For comparison, FePO4 microparticles (Figures S9 and S10) are also used to prepare SIB cathode by a similar method, which deliver inferior
electrochemical properties (Figure S11). Electrochemical impedance spectroscopy measurements show that FePO4 nanosheets demonstrate smaller diameter of high-frequency semicircle than FePO4 microparticles, implying smaller solidstate interface resistance (Figure S12). Furthermore, the amorphous FePO4 nanosheets can be operated with superior cycling stability at higher current rates of 100 and 200 mA g−1 (Figure S13). Apparently, a large reversible capacity of 83.5 and 68.5 mAh g−1 at 100 and 200 mA g−1 after 300 cycles can still be maintained, with a capacity retention of 87.1 and 84.6%, respectively. The stable cycling reversibility of amorphous FePO4 nanosheets is further verified by the SEM examinations of the electrode before and after 300 cycles at 100 mA g−1 demonstrated in Figure S14. There is no remarkable morphology change after long cycle testing at the high current density, suggesting a robust structure of the amorphous FePO4 nanosheets. The good rate property of the FePO4 nanosheets electrode is also studied by discharging and charging at different current densities varying from 10 to 1000 mA g−1 (Figure 6d). Remarkably, the FePO4 nanosheets manifest larger specific capacity and superior cycling stability than do the FePO4 microparticles at each current density. The average specific capacity for amorphous FePO4 nanosheets is 128.6, 113.1, 95.9, 85.8, 74.5, 57.3, and 42.1 mAh g−1 at 10, 20, 50, 100, 200, 500, and 1000 mA g−1, respectively. After operating at 1000 mA g−1 for ten cycles, a high capacity of about 128.3 mAh g−1 can still be recovered once the current rate is decreased back to 10 mA g−1, showing the outstanding structural stability of the amorphous FePO4 nanosheets. The above results clearly indicate that amorphous mesoporous structured nanosheets can significantly improve the sodium storage properties of FePO4 compared with the microparticles counterpart, which mainly stem from their unique structural advantages. In particular, the high surface area of the mesoporous nanosheet structure supplies larger electrolyte−electrode contact area and more active sites for Na+ insertion and surface sodium storage in comparison with the microparticles counterpart.52,66 The tiny size of primary nanoparticles and the existence of penetrable mesopores endue the much easier diffusion of Na+ ions by reducing the transportation length greatly.67 At the same time, the empty space in the nanosheets can buffer large bond distortion of the amorphous FePO4 upon Na+-ions uptake/release, which will help hold the structural integrity. Benefiting from the improved structural stability and kinetics, sodium storage performance of the present FePO4 nanosheets are thus considerably boosted.
4. CONCLUSIONS In summary, we have reported a simple templating approach for synthesizing mesoporous amorphous FePO4 nanosheets using GO nanosheets as removable templates. Uniform FePO4· 3H2O thin shells are first coated on the GO nanosheets to form GO@FePO4·3H2O core@shell structures. After subsequent elimination of GO cores and crystal water with air oxidation, high-quality amorphous FePO4 nanosheets are obtained. Benefiting from the high surface area, mesoporous thin nanosheets, and tiny primary nanoparticles, these FePO4 nanosheets exhibit greatly improved sodium storage performance with exceedingly stable specific capacity for over 300 cycles and boosted rate property at high current densities up to 1 A g−1. E
DOI: 10.1021/acsaem.8b01027 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX
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(12) Park, Y.-U.; Seo, D.-H.; Kwon, H.-S.; Kim, B.; Kim, J.; Kim, H.; Kim, I.; Yoo, H.-I.; Kang, K. A New High-Energy Cathode for a NaIon Battery with Ultrahigh Stability. J. Am. Chem. Soc. 2013, 135, 13870−13878. (13) Fang, Y.; Yu, X.-Y.; Lou, X. W. A Practical High-Energy Cathode for Sodium-Ion Batteries Based on Uniform P2-Na0.7CoO2 Microspheres. Angew. Chem., Int. Ed. 2017, 56, 5801−5805. (14) Wang, P.; Zhu, X.; Wang, Q.; Xu, X.; Zhou, X.; Bao, J. KelpDerived Hard Carbons as Advanced Anode Materials for Sodium-Ion Batteries. J. Mater. Chem. A 2017, 5, 5761−5769. (15) Wang, Q.; Zhu, X.; Liu, Y.; Fang, Y.; Zhou, X.; Bao, J. Rice Husk-Derived Hard Carbons as High-Performance Anode Materials for Sodium-Ion Batteries. Carbon 2018, 127, 658−666. (16) Zhou, X.; Guo, Y.-G. Highly Disordered Carbon as a Superior Anode Material for Room-Temperature Sodium-Ion Batteries. ChemElectroChem 2014, 1, 83−86. (17) Wang, P.; Qiao, B.; Du, Y.; Li, Y.; Zhou, X.; Dai, Z.; Bao, J. Fluorine-Doped Carbon Particles Derived from Lotus Petioles as High-Performance Anode Materials for Sodium-Ion Batteries. J. Phys. Chem. C 2015, 119, 21336−21344. (18) Jin, Y.; Sun, S.; Ou, M.; Liu, Y.; Fan, C.; Sun, X.; Peng, J.; Li, Y.; Qiu, Y.; Wei, P.; Deng, Z.; Xu, Y.; Han, J.; Huang, Y. HighPerformance Hard Carbon Anode: Tunable Local Structures and Sodium Storage Mechanism. ACS Appl. Energy Mater. 2018, 1, 2295− 2305. (19) Cao, Y.; Xiao, L.; Wang, W.; Choi, D.; Nie, Z.; Yu, J.; Saraf, L. V.; Yang, Z.; Liu, J. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Adv. Mater. 2011, 23, 3155−3160. (20) Gu, M.; Kushima, A.; Shao, Y.; Zhang, J.-G.; Liu, J.; Browning, N. D.; Li, J.; Wang, C. Probing the Failure Mechanism of SnO2 Nanowires for Sodium-Ion Batteries. Nano Lett. 2013, 13, 5203− 5211. (21) Luo, C.; Langrock, A.; Fan, X.; Liang, Y.; Wang, C. P2-Type Transition Metal Oxides for High Performance Na-Ion Battery Cathodes. J. Mater. Chem. A 2017, 5, 18214−18220. (22) Li, B.; Xi, B.; Feng, Z.; Lin, Y.; Liu, J.; Feng, J.; Qian, Y.; Xiong, S. Hierarchical Porous Nanosheets Constructed by Graphene-Coated, Interconnected TiO2 Nanoparticles for Ultrafast Sodium Storage. Adv. Mater. 2018, 30, 1705788. (23) Liu, Y.; Yu, X.-Y.; Fang, Y.; Zhu, X.; Bao, J.; Zhou, X.; Lou, X. W. Confining SnS2 Ultrathin Nanosheets in Hollow Carbon Nanostructures for Efficient Capacitive Sodium Storage. Joule 2018, 2, 725−735. (24) Tu, F.; Xu, X.; Wang, P.; Si, L.; Zhou, X.; Bao, J. A Few-Layer SnS2/Reduced Graphene Oxide Sandwich Hybrid for Efficient Sodium Storage. J. Phys. Chem. C 2017, 121, 3261−3269. (25) Jiang, Y.; Guo, Y.; Lu, W.; Feng, Z.; Xi, B.; Kai, S.; Zhang, J.; Feng, J.; Xiong, S. Rationally Incorporated MoS2/SnS2 Nanoparticles on Graphene Sheets for Lithium-Ion and Sodium-Ion Batteries. ACS Appl. Mater. Interfaces 2017, 9, 27697−27706. (26) Jiang, Y.; Feng, Y.; Xi, B.; Kai, S.; Mi, K.; Feng, J.; Zhang, J.; Xiong, S. Ultrasmall SnS2 Nanoparticles Anchored on WellDistributed Nitrogen-Doped Graphene Sheets for Li-Ion and NaIon Batteries. J. Mater. Chem. A 2016, 4, 10719−10726. (27) Park, S. I.; Gocheva, I.; Okada, S.; Yamaki, J.-i. Electrochemical Properties of NaTi2(PO4)3 Anode for Rechargeable Aqueous SodiumIon Batteries. J. Electrochem. Soc. 2011, 158, A1067−A1070. (28) Jian, Z.; Zhao, L.; Pan, H.; Hu, Y.-S.; Li, H.; Chen, W.; Chen, L. Carbon Coated Na3V2(PO4)3 as Novel Electrode Material for Sodium Ion Batteries. Electrochem. Commun. 2012, 14, 86−89. (29) Yun, J.; Schiegg, F. A.; Liang, Y.; Scieszka, D.; Garlyyev, B.; Kwiatkowski, A.; Wagner, T.; Bandarenka, A. S. Electrochemically Formed NaxMn[Mn(CN)6] Thin Film Anodes Demonstrate Sodium Intercalation and Deintercalation at Extremely Negative Electrode Potentials in Aqueous Media. ACS Appl. Energy Mater. 2018, 1, 123− 128.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsaem.8b01027. AFM image, C 1s XPS spectrum, SEM and TEM images; N2 sorption isotherms and corresponding poresize distributions, FT-IR spectra, TGA analysis, EDX spectrum, high-current-density cycling performance, XRD pattern, electrochemical characterization, EIS spectra, and comparison of sodium storage properties (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Xiaosi Zhou: 0000-0001-9641-7166 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Grant Nos. 51577094 and 21503112) and the 100 Talents Program of Nanjing Normal University.
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REFERENCES
(1) Ong, S. P.; Chevrier, V. L.; Hautier, G.; Jain, A.; Moore, C.; Kim, S.; Ma, X.; Ceder, G. Voltage, Stability and Diffusion Barrier Differences between Sodium-Ion and Lithium-Ion Intercalation Materials. Energy Environ. Sci. 2011, 4, 3680−3688. (2) Slater, M. D.; Kim, D.; Lee, E.; Johnson, C. S. Sodium-Ion Batteries. Adv. Funct. Mater. 2013, 23, 947−958. (3) Zhou, X.; Yu, L.; Lou, X. W. Formation of Uniform N-Doped Carbon-Coated SnO2 Submicroboxes with Enhanced Lithium Storage Properties. Adv. Energy Mater. 2016, 6, 1600451. (4) Wu, C.; Maier, J.; Yu, Y. Generalizable Synthesis of MetalSulfides/Carbon Hybrids with Multiscale, Hierarchically Ordered Structures as Advanced Electrodes for Lithium Storage. Adv. Mater. 2016, 28, 174−180. (5) Palomares, V.; Serras, P.; Villaluenga, I.; Hueso, K. B.; CarreteroGonzalez, J.; Rojo, T. Na-Ion Batteries, Recent Advances and Present Challenges to Become Low Cost Energy Storage Systems. Energy Environ. Sci. 2012, 5, 5884−5901. (6) Zhou, X.; Guo, Y.-G. A PEO-Assisted Electrospun SiliconGraphene Composite as an Anode Material for Lithium-Ion Batteries. J. Mater. Chem. A 2013, 1, 9019−9023. (7) Li, T.; Wang, A.; Li, X.; Wang, J.; Zhang, J.; Fu, G.; Xu, L.; Sun, D.; Tang, Y. MoS0.5Se1.5 Embedded in 2D Porous Carbon Sheets Boost Lithium Storage Performance as an Anode Material. Adv. Mater. Interfaces 2018, 5, 1701604. (8) Mao, J.; Zhou, T.; Zheng, Y.; Gao, H.; Liu, H. K.; Guo, Z. TwoDimensional Nanostructures for Sodium-Ion Battery Anodes. J. Mater. Chem. A 2018, 6, 3284−3303. (9) Kim, S.-W.; Seo, D.-H.; Ma, X.; Ceder, G.; Kang, K. Electrode Materials for Rechargeable Sodium-Ion Batteries: Potential Alternatives to Current Lithium-Ion Batteries. Adv. Energy Mater. 2012, 2, 710−721. (10) Shi, L.; Zhao, T. Recent Advances in Inorganic 2D Materials and Their Applications in Lithium and Sodium Batteries. J. Mater. Chem. A 2017, 5, 3735−3758. (11) Zhang, J.; Qi, L.; Zhu, X.; Yan, X.; Jia, Y.; Xu, L.; Sun, D.; Tang, Y. Proline-Derived in Situ Synthesis of Nitrogen-Doped Porous Carbon Nanosheets with Encaged Fe2O3@Fe3C Nanoparticles for Lithium-Ion Battery Anodes. Nano Res. 2017, 10, 3164−3177. F
DOI: 10.1021/acsaem.8b01027 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX
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ACS Applied Energy Materials
(49) Duan, S.-Y.; Piao, J.-Y.; Zhang, T.-Q.; Sun, Y.-G.; Liu, X.-C.; Cao, A.-M.; Wan, L.-J. Kinetically Controlled Formation of Uniform FePO4 Shells and Their Potential for Use in High-Performance Sodium Ion Batteries. NPG Asia Mater. 2017, 9, No. e414. (50) Liu, Y.; Xu, Y.; Han, X.; Pellegrinelli, C.; Zhu, Y.; Zhu, H.; Wan, J.; Chung, A. C.; Vaaland, O.; Wang, C.; Hu, L. Porous Amorphous FePO4 Nanoparticles Connected by Single-Wall Carbon Nanotubes for Sodium Ion Battery Cathodes. Nano Lett. 2012, 12, 5664−5668. (51) Butler, S. Z.; Hollen, S. M.; Cao, L. Y.; Cui, Y.; Gupta, J. A.; Gutierrez, H. R.; Heinz, T. F.; Hong, S. S.; Huang, J. X.; Ismach, A. F.; Johnston-Halperin, E.; Kuno, M.; Plashnitsa, V. V.; Robinson, R. D.; Ruoff, R. S.; Salahuddin, S.; Shan, J.; Shi, L.; Spencer, M. G.; Terrones, M.; Windl, W.; Goldberger, J. E. Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene. ACS Nano 2013, 7, 2898−2926. (52) Wang, L.; Yang, H.; Shu, T.; Xin, Y.; Chen, X.; Li, Y.; Li, H.; Hu, X. Nanoengineering S-Doped TiO2 Embedded Carbon Nanosheets for Pseudocapacitance-Enhanced Li-Ion Capacitors. ACS Appl. Energy Mater. 2018, 1, 1708−1715. (53) Jiang, Y.; Wei, M.; Feng, J.; Ma, Y.; Xiong, S. Enhancing the Cycling Stability of Na-Ion Batteries by Bonding SnS2 Ultrafine Nanocrystals on Amino-Functionalized Graphene Hybrid Nanosheets. Energy Environ. Sci. 2016, 9, 1430−1438. (54) Hummers, W. S.; Offeman, R. E. Preparation of Graphitic Oxide. J. Am. Chem. Soc. 1958, 80, 1339−1339. (55) Wang, H.; Liu, L.; Wang, R.; Zhang, D.; Zhu, L.; Qiu, S.; Wei, Y.; Jin, X.; Zhang, Z. Design and Synthesis of High Performance LiFePO4/C Nanomaterials for Lithium Ion Batteries Assisted by a Facile H+/Li+ Ion Exchange Reaction. J. Mater. Chem. A 2015, 3, 8062−8069. (56) Kim, S.-W.; Ryu, J.; Park, C. B.; Kang, K. Carbon NanotubeAmorphous FePO4 Core-Shell Nanowires as Cathode Material for Li Ion Batteries. Chem. Commun. 2010, 46, 7409−7411. (57) Li, N.-W.; Yin, Y.-X.; Guo, Y.-G. Three-Dimensional SandwichType Graphene@Microporous Carbon Architecture for LithiumSulfur Batteries. RSC Adv. 2016, 6, 617−622. (58) Yao, H.-R.; Yin, Y.-X.; Guo, Y.-G. Size Effects in Lithium Ion Batteries. Chin. Phys. B 2016, 25, 018203. (59) Xu, G.-L.; Xu, Y.-F.; Sun, H.; Fu, F.; Zheng, X.-M.; Huang, L.; Li, J.-T.; Yang, S.-H.; Sun, S.-G. Facile Synthesis of Porous MnO/C Nanotubes as a High Capacity Anode Material for Lithium Ion Batteries. Chem. Commun. 2012, 48, 8502−8504. (60) Zeng, L.; Li, X.; Shi, Y.; Qi, Y.; Huang, D.; Tade, M.; Wang, S.; Liu, S. FePO4 Based Single Chamber Air-Cathode Microbial Fuel Cell for Online Monitoring Levofloxacin. Biosens. Bioelectron. 2017, 91, 367−373. (61) Liu, Y.; Zhou, Y.; Zhang, J.; Xia, Y.; Chen, T.; Zhang, S. Monoclinic Phase Na3Fe2(PO4)3: Synthesis, Structure, and Electrochemical Performance as Cathode Material in Sodium-Ion Batteries. ACS Sustainable Chem. Eng. 2017, 5, 1306−1314. (62) Zhu, Y.; Wang, C. Novel CV for Phase Transformation Electrodes. J. Phys. Chem. C 2011, 115, 823−832. (63) Nishimura, S.-i.; Natsui, R.; Yamada, A. Superstructure in the Metastable Intermediate-Phase Li2/3FePO4 Accelerating the Lithium Battery Cathode Reaction. Angew. Chem., Int. Ed. 2015, 54, 8939− 8942. (64) Peng, J.; Wang, J.; Yi, H.; Hu, W.; Yu, Y.; Yin, J.; Shen, Y.; Liu, Y.; Luo, J.; Xu, Y.; Wei, P.; Li, Y.; Jin, Y.; Ding, Y.; Miao, L.; Jiang, J.; Han, J.; Huang, Y. A Dual-Insertion Type Sodium-Ion Full Cell Based on High-Quality Ternary-Metal Prussian Blue Analogs. Adv. Energy Mater. 2018, 8, 1702856. (65) Yu, X.-Y.; Wu, H. B.; Yu, L.; Ma, F.-X.; Lou, X. W. Rutile TiO2 Submicroboxes with Superior Lithium Storage Properties. Angew. Chem., Int. Ed. 2015, 54, 4001−4004. (66) Bommier, C.; Ji, X. Electrolytes, SEI Formation, and Binders: A Review of Nonelectrode Factors for Sodium-Ion Battery Anodes. Small 2018, 14, 1703576. (67) Lai, H.; Shang, L.; Wu, Q.; Yang, L.; Zhao, J.; Li, H.; Lyu, Z.; Wang, X.; Hu, Z. Spinel Nickel Cobaltite Mesostructures Assembled
(30) Lu, Y.; Wang, L.; Cheng, J.; Goodenough, J. B. Prussian Blue: A New Framework of Electrode Materials for Sodium Batteries. Chem. Commun. 2012, 48, 6544−6546. (31) Liu, X.; Du, Y.; Xu, X.; Zhou, X.; Dai, Z.; Bao, J. Enhancing the Anode Performance of Antimony through Nitrogen-Doped Carbon and Carbon Nanotubes. J. Phys. Chem. C 2016, 120, 3214−3220. (32) Wu, L.; Hu, X.; Qian, J.; Pei, F.; Wu, F.; Mao, R.; Ai, X.; Yang, H.; Cao, Y. Sb-C Nanofibers with Long Cycle Life as an Anode Material for High-Performance Sodium-Ion Batteries. Energy Environ. Sci. 2014, 7, 323−328. (33) Liu, Z.; Yu, X.-Y.; Lou, X. W.; Paik, U. Sb@C Coaxial Nanotubes as a Superior Long-Life and High-Rate Anode for Sodium Ion Batteries. Energy Environ. Sci. 2016, 9, 2314−2318. (34) Xu, X.; Si, L.; Zhou, X.; Tu, F.; Zhu, X.; Bao, J. Chemical Bonding between Antimony and Ionic Liquid-Derived NitrogenDoped Carbon for Sodium-Ion Battery Anode. J. Power Sources 2017, 349, 37−44. (35) Liu, Y.; Xiao, X.; Fan, X.; Li, M.; Zhang, Y.; Zhang, W.; Chen, L. GeP5/C Composite as Anode Material for High Power Sodium-Ion Batteries with Exceptional Capacity. J. Alloys Compd. 2018, 744, 15− 22. (36) Fan, X.; Mao, J.; Zhu, Y.; Luo, C.; Suo, L.; Gao, T.; Han, F.; Liou, S.-C.; Wang, C. Superior Stable Self-Healing SnP3 Anode for Sodium-Ion Batteries. Adv. Energy Mater. 2015, 5, 1500174. (37) Fan, X.; Gao, T.; Luo, C.; Wang, F.; Hu, J.; Wang, C. Superior Reversible Tin Phosphide-Carbon Spheres for Sodium Ion Battery Anode. Nano Energy 2017, 38, 350−357. (38) Zhu, Y.; Xu, Y.; Liu, Y.; Luo, C.; Wang, C. Comparison of Electrochemical Performances of Olivine NaFePO4 in Sodium-Ion Batteries and Olivine LiFePO4 in Lithium-Ion Batteries. Nanoscale 2013, 5, 780−787. (39) Rahman, M. M.; Sultana, I.; Mateti, S.; Liu, J.; Sharma, N.; Chen, Y. Maricite NaFePO4/C/Graphene: A Novel Hybrid Cathode for Sodium-Ion Batteries. J. Mater. Chem. A 2017, 5, 16616−16621. (40) Barpanda, P.; Ye, T.; Nishimura, S.-i.; Chung, S.-C.; Yamada, Y.; Okubo, M.; Zhou, H.; Yamada, A. Sodium Iron Pyrophosphate: A Novel 3.0 V Iron-Based Cathode for Sodium-Ion Batteries. Electrochem. Commun. 2012, 24, 116−119. (41) Chen, X.; Du, K.; Lai, Y.; Shang, G.; Li, H.; Xiao, Z.; Chen, Y.; Li, J.; Zhang, Z. In-Situ Carbon-Coated Na2FeP2O7 Anchored in Three-Dimensional Reduced Graphene Oxide Framework as a Durable and High-Rate Sodium-Ion Battery Cathode. J. Power Sources 2017, 357, 164−172. (42) Fang, Y.; Xiao, L.; Qian, J.; Ai, X.; Yang, H.; Cao, Y. Mesoporous Amorphous FePO4 Nanospheres as High-Performance Cathode Material for Sodium-Ion Batteries. Nano Lett. 2014, 14, 3539−3543. (43) Yang, G.; Ding, B.; Wang, J.; Nie, P.; Dou, H.; Zhang, X. Excellent Cycling Stability and Superior Rate Capability of a Graphene-Amorphous FePO4 Porous Nanowire Hybrid as a Cathode Material for Sodium Ion Batteries. Nanoscale 2016, 8, 8495−8499. (44) Oh, S. W.; Myung, S.-T.; Oh, S.-M.; Oh, K. H.; Amine, K.; Scrosati, B.; Sun, Y.-K. Double Carbon Coating of LiFePO4 as High Rate Electrode for Rechargeable Lithium Batteries. Adv. Mater. 2010, 22, 4842−4845. (45) Oh, S.-M.; Myung, S.-T.; Hassoun, J.; Scrosati, B.; Sun, Y.-K. Reversible NaFePO4 Electrode for Sodium Secondary Batteries. Electrochem. Commun. 2012, 22, 149−152. (46) Zaghib, K.; Trottier, J.; Hovington, P.; Brochu, F.; Guerfi, A.; Mauger, A.; Julien, C. M. Characterization of Na-Based Phosphate as Electrode Materials for Electrochemical Cells. J. Power Sources 2011, 196, 9612−9617. (47) Casas-Cabanas, M.; Roddatis, V. V.; Saurel, D.; Kubiak, P.; Carretero-Gonzalez, J.; Palomares, V.; Serras, P.; Rojo, T. Crystal Chemistry of Na Insertion/Deinsertion in FePO4-NaFePO4. J. Mater. Chem. 2012, 22, 17421−17423. (48) Liu, Y.; Xu, S.; Zhang, S.; Zhang, J.; Fan, J.; Zhou, Y. Direct Growth of FePO4/Reduced Graphene Oxide Nanosheet Composites for the Sodium-Ion Battery. J. Mater. Chem. A 2015, 3, 5501−5508. G
DOI: 10.1021/acsaem.8b01027 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX
Article
ACS Applied Energy Materials from Ultrathin Nanosheets for High-Performance Electrochemical Energy Storage. ACS Appl. Energy Mater. 2018, 1, 684−691.
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DOI: 10.1021/acsaem.8b01027 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX
