Fluorine-Doped Carbon Particles Derived from Lotus Petioles as High

Article pubs.acs.org/JPCC

Fluorine-Doped Carbon Particles Derived from Lotus Petioles as High-Performance Anode Materials for Sodium-Ion Batteries Pengzi Wang,† Bin Qiao,† Yichen Du, Yafei Li, Xiaosi Zhou,* Zhihui Dai,* and Jianchun Bao Jiangsu Key Laboratory of Biofunctional Materials, School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, P. R. China

Downloaded by UNIV OF PRINCE EDWARD ISLAND on September 5, 2015 | http://pubs.acs.org Publication Date (Web): September 4, 2015 | doi: 10.1021/acs.jpcc.5b05443

S Supporting Information *

ABSTRACT: In contrast to the extensive investigation of the electrochemical performance of conventional carbon materials in sodium-ion batteries, there has been scarcely any study of sodium storage property of fluorine-doped carbon. Here we report for the first time the application of fluorine-doped carbon particles (F-CP) synthesized through pyrolysis of lotus petioles as anode materials for sodium-ion batteries. Electrochemical tests demonstrate that the F-CP electrode delivers an initial charge capacity of 230 mA h g−1 at a current density of 50 mA g−1 between 0.001 and 2.8 V, which greatly outperforms the corresponding value of 149 mA h g−1 for the counterpart banana peels-derived carbon (BPC). Even under 200 mA g−1, the F-CP electrode could still exhibit a charge capacity of 228 mA h g−1 with initial charge capacity retention of 99.1% after 200 cycles compared to the BPC electrode with 107 mA h g−1 and 71.8%. The F-doping and the large interlayer distance as well as the disorder structure contribute to a lowering of the sodium ion insertion−extraction barrier, thus promoting the Na+ diffusion and providing more active sites for Na+ storage. In specific, the F-CP electrode shows longer low-discharge-plateau and better kinetics than does the common carbon-based electrode. The unique electrochemical performance of F-CP enriches the existing knowledge of the carbon-based electrode materials and broadens avenues for rational design of anode materials in sodium-ion batteries.

1. INTRODUCTION Currently, lithium-ion batteries have been widely used as the rechargeable energy source of choice in various portable electronic devices due to their high energy density and long cycle life.1 The ever-increasing demand for them in large-scale application, including hybrid electric vehicles (HEVs) and electric vehicles (EVs), has sparked the research in advanced battery systems with low cost and high electrochemical performance.2 Sodium-ion batteries, which employ earthabundant inexpensive sodium, have recently attracted considerable attention as a promising alternative to LIBs.3−6 To date, limited anode materials have been developed for sodium-ion batteries while a lot of suitable cathode materials, including Na0.71CoO2, Nax[Fe1/2Mn1/2]O2, NaMO2 (M = Fe, Ni), NaNi1/3M1/3Mn1/3O2 (M = Fe, Co), NaFeF3, NaMPO4 (M = Fe, Mn), Na2FePO4F, Na2FeP2O7, Na3V2(PO4)3, Na3Ni2SbO6, and Na2MnFe(CN)6·zH2O were identified.7−21 Therefore, one of the urgent issues for the practical applications of sodium-ion batteries is to obtain appropriate anode materials. Because of their abundance, low cost, environmental benignity, thermal stability, and electrical conductivity, carbon materials have been considered as the most promising candidates among the recently reported anode materials for sodium-ion batteries, such as Na2Ti3O7, Li4Ti5O12, MoS2, Sn, Sb/C, and P/C.22−30 However, the widely used commercial graphite anode has been reported to display a low reversible capacity when used for sodium storage (Supporting Information, Table S1).31,32 In © XXXX American Chemical Society

contrast, some synthetic carbon-based materials, including hard carbon,33−43 carbon black,44 petroleum coke,45 carbon nanowires,46,47 reduced graphene oxide,48,49 porous carbon/ graphene composites,50,51 banana peel pseudographite,52 and graphene foams,53 were proved to facilitate sodium-ion insertion−extraction.54−69 In the previous studies, the increasement of the electrochemical performance of sodium-ion batteries mainly relies on the interlayer distance of carbon materials in anodes.70−74 In addition, heteroatom doping has been demonstrated as an effective strategy to facilitate the charge transfer and electrode−electrolyte interactions of a carbon-based electrode through ameliorating the electrical conductivity and surface wettability.75 In this regard, N-doped carbons have been extensively studied as the anode materials for sodium-ion batteries. For instance, Huang and co-workers reported N-doped porous carbon nanofibers that delivered a capacity of 134.2 mA h g−1 with 88.7% capacity retention after 200 cycles at a current density of 200 mA g−1 in the voltage range of 0.01−2 V.47 Zhang et al. developed N-doped porous carbon nanosheets that showed a reversible capacity of 155.2 mA h g−1 with ∼45% capacity retention even after 260 cycles under 50 mA g−1 between 0.01 and 3.0 V.51 More recently Xu et al. prepared 3D N-doped graphene foams with 6.8 at% Received: June 8, 2015 Revised: July 24, 2015

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DOI: 10.1021/acs.jpcc.5b05443 J. Phys. Chem. C XXXX, XXX, XXX−XXX

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The Journal of Physical Chemistry C nitrogen that showed a high charge capacity of 594 mA h g−1 with 69.7% capacity retention after 150 cycles at a current density of 500 mA g−1 in the voltage range of 0.02−3 V.53 Therefore, heteroatom-doped carbon materials are extremely promising for future sodium-ion battery applications. Recently chlorine, bromine, or iodine-doped graphene nanoplatelets have been demonstrated to be attractive carbon materials for lithium storage, as the unique edge-selectively halogenated structure could boost lithium ion insertion/ extraction at the edges between graphitic layers.76 Herein, we report for the first time the use of fluorine-doped carbon particles (F-CP) prepared by pyrolysis of lotus petioles as anode materials for sodium-ion batteries. For comparison, banana peels-derived carbon (BPC) was also fabricated by carbonization of banana peels under the same conditions and graphite flakes (GF) were used as received. This method employed the renewable lotus petioles as a precursor to allow for a low-cost and large-scale production of F-CP. It was found that F-CP electrode showed an initial charge capacity of 230 mA h g−1 at a current density of 50 mA g−1 in the voltage range of 0.001−2.8 V, which was higher than the referred BPC electrode with 149 mA h g−1. Moreover, the F-CP electrode exhibited a higher charge capacity of 228 mA h g−1 under 200 mA g−1 with a higher capacity retention of 99.1% than the BPC electrode with 107 mA h g−1 and 71.8% after 200 cycles, respectively. Even at 500 mA g−1 the F-CP electrode still maintained a reversible capacity of 141 mA h g−1 and more than 89.2% capacity retention after 300 cycles, suggesting a remarkably high cycling stability. Such outstanding electrochemical performance of F-CP as anode materials for sodiumion batteries is due to the high electronegativity of F (χ = 3.98 higher than χ = 2.55 for carbon), the large interlayer distance (0.40 nm), as well as the disorder structure, all of which result in improved sodium ion transport through the electrolyte and electrode upon cycling.

microscopy (TEM) and high-resolution TEM (HRTEM) observations were conducted on a JEOL JEM-2100F transmission electron microscope operated at 200 kV. X-ray photoelectron spectroscopy (XPS) was obtained on an ESCALab250Xi electron spectrometer from VG Scientific using 300 W Al Kα radiation. Thermogravimetric (TG) and differential scanning calorimetry (DSC) studies were carried out on a NETZSCH STA 449 F3 under air flow with a heating rate of 10 °C min−1 from room temperature to 1000 °C. X-ray diffraction (XRD) patterns were acquired on a Rigaku D/max 2500/PC diffractometer using Cu Kα radiation. Raman spectra were measured on a Labram HR800 with a laser wavelength of 514.5 nm. Nitrogen adsorption and desorption isotherms at 77.3 K were collected on an ASAP 2050 surface area-pore size analyzer. Secondary ion mass spectroscopy (SIMS) measurements were determined by a time-of-flight secondary ion mass spectrometer TOF-SIMS 5 from ION-TOF GmbH (Munster, Germany). A Bi1+ liquid metal ion gun operating at a 30 keV beam voltage with a 45° incident angle was applied. All analyses were carried out on selected area of 500 × 500 μm2 at 256 × 256 pixels after two prescans under DC mode to get rid of most of the surface contaminants. Charge compensation with an electron flood gun was employed during the analysis cycles. Negative ion mode spectra were calibrated on the C−, CH−, CH2−, C2−, and C2H− peaks. 2.3. Electrochemical Measurements. Electrochemical performances were evaluated by using CR2032 coin cells. To produce working electrodes, F-CP was mixed with Super-P carbon black and poly(vinylidene fluoride) with a weight ratio of 80:10:10 in N-methyl-2-pyrrolidone using a mortar and pestle. The resulting homogeneous slurry was pasted onto pure Cu foil (99.9%, Goodfellow) and then dried in a vacuum oven at 80 °C for 10 h, resulting in electrodes with a typical mass loading of 1.0−1.5 mg cm−2. The electrolyte was 1 M NaClO4 dissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate(DEC) with a volume ratio of 1:1. Glass fibers from Whatman and pure sodium metal foil were utilized as separators and counter electrode, respectively. All coin cells were assembled in an argon-filled glovebox (H2O, O2 < 0.1 ppm, MBraun, Germany). The charge−discharge measurements of the cells were galvanostatically performed on a Land CT2001A multichannel battery testing system in the fixed voltage range of 0.001−2.8 V vs Na+/Na at room temperature. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were carried out on a PARSTAT 4000 electrochemical workstation. CV was conducted at a scan rate of 0.1 mV s−1 while EIS was collected by applying a sine wave with amplitude of 10.0 mV over the frequency range from 100 kHz to 10 mHz. 2.4. DFT Calculations. The DFT computations employed an all-electron method within a generalized gradient approximation (GGA) for the exchange-correlation term, as implemented in the DMol3 code.77,78 The double numerical plus polarization (DNP) basis set and PBE functional79 were adopted in all computations. It is known that weak interactions are out of the framework of standard PBE functional, so we adopted the PBE+D2 (D stands for dispersion) method with the Grimme vdW correction.80 Self-consistent field (SCF) calculations were performed with a convergence criterion of 10−6 au on the total energy and electronic computations. The Brillouin zone was sampled with a 6 × 6 × 1 Γ centered k points setting in geometry optimizations.

2. EXPERIMENTAL SECTION 2.1. Synthesis Fluorine-Doped Carbon Particles (FCP). F-CP was prepared from lotus petioles through a modified Mitlin’s method.52 Typically, lotus petioles were first collected from a campus pond, washed with deionized (DI) water, split into small pieces, and dried under vacuum at 120 °C overnight. Then 1.25 g of dried lotus bar was placed in a crucible in a tubular furnace, heated to 1100 °C, and kept at that temperature for 5 h under argon atmosphere with a heating rate of 5 °C min−1. The resulting carbon was washed separately in 5 M KOH and 2 M HCl, both at 60 °C, under vigorous stirring to eliminate the impurities. The purified sample was collected by centrifugation, washed with DI water, and dried under vacuum at 120 °C overnight. Afterward, the carbon was further activated at 300 °C for 5 h in the tube furnace in an air flow. The resultant product was washed three times by 2 M HCl and two times with DI water again before drying at 120 °C under vacuum overnight. Finally, F-CP was obtained after grinding for 30 min and dried under vacuum at 70 °C overnight. For comparison, banana peels-derived carbon (BPC) was prepared following the same procedure as for F-CP except that banana peels (Yunnan, China) was employed as the biomass precursor. Graphite flakes (GF) (Alfa Aesar, 325 mesh) were used without further purification. 2.2. Material Characterization. Scanning electron microscopy (SEM) was performed using a JEOL JSM-7600F scanning electron microscope operated at 10 kV. Transmission electron B


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Figure 1. (a, d, g) SEM, TEM, and HRTEM images of GF. (b, e, h) SEM, TEM, and HRTEM images of BPC. (c, f, i) SEM, TEM, and HRTEM images of F-CP. Insets of d−f are the SAED patterns of GF, BPC, and F-CP, respectively.

3. RESULTS AND DISCUSSION To analyze the morphology of the materials studied, we carried out SEM and TEM characterizations. SEM and TEM images of GF (Figure 1a,d), BPC (Figure 1b,e), and F-CP (Figure 1c,f) show that the typical particle size of F-CP (Supporting Information, Figure S1) and BPC produced from pyrolysis are less than 10 μm, while GF is up to 40 μm. The diffused rings displayed in the associated selected area electron diffraction (SAED) patterns (insets of Figure 1e,f) suggest the formation of small crystalline domains dispersed in the amorphous matrix. The partial crystallization of F-CP and BPC was further confirmed by HRTEM observations. The corresponding HRTEM images in Figure 1h,i show largely disordered structures for F-CP and BPC. As can be seen, their respective interlayer distance can be estimated to be around 0.40 and 0.40 nm in the crystalline domains, suggesting that the lattice spacing of F-CP and BPC are larger than that of commercial graphite flakes (0.34 nm, Figure 1g), which are

favorable for enhancing the sodium storage properties of F-CP and BPC. A comparison of HRTEM images between F-CP and BPC indicates that the F-doped sample possesses a more loosely packed graphitic layers, which could lead to a higher sodium ion storage in the F-CP electrode during Na uptake/ release processes. Besides, nitrogen absorption measurements determine Brunauer−Emmett−Teller (BET) surface area of 46.4 m2 g−1 for F-CP, which is much lower than that of BPC (763.3 m2 g−1, Supporting Information, Figure S2). The low surface area of F-CP usually results in excellent electrode packing characteristics, high volumetric capacities, and low levels of solid electrolyte interphase (SEI) formation. SIMS measurements were performed on F-CP, BPC, and GF after most of their surface contaminants were removed (Figures 2a and S3, Supporting Information). The result shows that obvious F− peak can be observed in the F-CP sample but does not exist in the BPC or GF sample, implying that only lotus petioles-derived carbon particles is probably F-doped. Figure 2b C


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Figure 2. (a) SIMS spectra of F-CP, BPC, and GF. (b) XPS survey scan of F-CP. (c) XRD patterns of F-CP, BPC, and GF. (d) Raman spectra of FCP, BPC, and GF. Inset of part b is the high-resolution XPS F 1s spectrum of F-CP.

Figure 3. (a) Initial charge−discharge profiles of the GF, BPC, and F-CP electrodes at 0.05 A g−1. (b) Rate capabilities of the GF, BPC, and F-CP electrodes from 0.05 to 10 A g−1. (c) Capacity retentions of the initial capacities at 0.05 A g−1 versus current density. (d) Cycling performances of the GF, BPC, and F-CP electrodes in the voltage range of 0.001−2.8 V. The first 10 cycles are under 0.05 A g−1, and the remaining 190 cycles are under 0.2 A g−1.

stability of F-CP, as exemplified by a decrease in the decomposition temperature from 743.2 °C for GF and 582.0 °C for BPC to 562.8 °C for F-CP, probably owing to the doping-induced reduction process (Supporting Information, Figure S5).53 X-ray diffraction (XRD) profiles for F-CP, BPC, and GF are displayed in Figure 2c. As can be seen, characteristic (002) peaks for graphitic carbon appeared at 22.4°, 22.5°, and 26.5° for the F-CP, BPC, and GF, corresponding to interlayer distances (d-spacing) of 0.40, 0.40, and 0.34 nm, respectively, consistent with the HRTEM observations. Compared with an

shows the XPS survey spectrum of the F-CP sample, which reveals 1.1 at % fluorine in F-CP (Supporting Information, Table S2). As displayed in the inset of Figure 2b, the highresolution XPS F 1s spectrum of the sample further verify the existence of F-doping in F-CP. In addition, the deconvolution of the C 1s XPS peak is demonstrated in Figure S4 (Supporting Information). Peaks centered at 284.8, 285.4, 285.9, 286.7, and 289.6 eV can be ascribed to the carbon atoms in sp2-C, sp3-C, C−O, C−F bonds,81 shakeup of sp2-C, respectively. TG and DSC profiles further show that F-doping weakened thermal D


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than that for BPC (4.4%) or GF (5.7%) as well. Furthermore, an increase of specific capacity of the F-CP electrode can be observed during the initial cycles. This activation process may be originated from the delayed infiltration of the electrolyte into the carbon particles.27 Figure 3d displays the relatively long-term cycling performance for the F-CP, BPC, and GF electrodes measured under 200 mA g−1 in the voltage range of 0.001−2.8 V. Obviously, the F-CP, BPC, and GF electrodes deliver the first charge/ discharge capacities of 230/440, 149/485, and 29/128 mA h g−1 with initial Coulombic efficiencies of 52.3%, 30.7%, and 22.7%, respectively. The poor Coulombic efficiency of the first cycle is mainly attributed to the reductive decomposition of the electrolyte and the formation of SEI layer, and irreversible reactions between sodium ions and the residual oxygencontaining functional groups of the carbon particles. After 200 cycles, the F-CP, BPC, and GF electrodes still exhibit charge/discharge capacities of 228/229, 106/107, and 16.1/ 16.3 mA h g−1 within the initial capacity retention of 99.4%/ 52.0%, 71.1%/22.1%, and 55.5%/12.7%, respectively. Although the relatively low Coulombic efficiencies for the F-CP, BPC, and GF in the first cycle, all electrodes show a much higher average Coulombic efficiency of 99.0% for F-CP, 98.2% for BPC, and 97.9% for GF over 200 cycles (Supporting Information, Figure S7). The charge/discharge capacities, capacity retention, and Coulombic efficiency observed for FCP are higher than those of BPC or GF, suggesting that the FCP electrode possesses a better sodium storage properties in comparison with the BPC or GF electrode. Moreover, as shown in Figure S8 (Supporting Information), the F-CP electrode still can exhibit a stable capacity of 126 mA h g−1 at a rate of 500 mA g−1 after 300 cycles, showing an outstanding high-rate cycling stability. To gain a better understanding of the observed superior electrochemical performance for F-CP, we performed ab initio simulation using density functional theory and electrochemical impedance spectroscopy (EIS). Figure 4a shows the geometric structure of the crystalline domain of F-CP. In general, the heteroatom-doping is prone to increase the repulsive interaction between carbon layers, thus enlarging the interlayer distance. For simplicity, we employed the F-doped graphene sheets as the model to calculate the interlayer distance of graphitic layer. On the basis of the atomic ratio of C to F is ∼84 from the XPS measurement, the interplanar spacing is calculated to be around 0.41 nm, which plays an important role in improving Na+ tansportation and storage. Figure 4b shows the electrochemical impedance spectra for the F-CP cell, measured before cycling as well as after 30, 100, and 200 cycles. The EIS measurements of the F-CP cell show that the gradually stabilized impedance upon cycling can probably be attributed to the delayed infiltration of electrolyte into the carbon particles, in good agreement with the cycling performance (Figure 3d). Furthermore, we carried out SEM and HRTEM analysis of the F-CP electrode material after the 30th, 100th, and 200th cycle (Figure 5). The SEM images (Figure 5a−c) indicate that the FCP electrode−electrolyte interface is stable and the formation of SEI layer is negligible. The HRTEM images and corresponding SAED patterns (Figure 5d−f) show that the lattice spacing of F-CP is well maintained during 200 discharge−charge cycles, suggesting an intercalation mechanism is dominant in a Na/F-CP battery with cutoff voltage between 0.001 and 2.8 V. Because of the high electronegativity from F-doping, the repulsion for Na+ insertion and extraction is

interlayer spacing of 0.34 nm for GF, the resulting larger interlayer spacing of the F-CP and BPC samples is significantly important for the insertion−extraction behavior of relatively large sodium ion. Figure 2d shows Raman spectra of the F-CP, BPC, and GF, all of which presented the remarkable D and G bands at around 1355 and 1602 cm−1, respectively. The F-CP sample displays the highest peak intensity ratio of D to G band (ID/IG = 1.01), which is probably due to its disordered structure further enhanced by F-doping. All of the F-doping and large interlayer distance as well as disordered structure of F-CP could lead to high capacity and excellent performance when they are evaluated for sodium storage. Figure 3a shows the initial charge/discharge profiles for the F-CP, BPC, and GF electrodes at a current density of 50 mA g−1 in the voltage range of 0.001−2.8 V vs Na+/Na, which show apparent plateaus during the first discharge process for all of the three electrodes. We note that the second discharge plateau at ∼0.02 V for F-CP is longer with respect to that for BPC or GF in the first cycle, indicating that a larger number of sodium ions have inserted into the interlayer of F-CP during the discharge process. This phenomenon was further verified by cyclic voltammetry (CV) measurements. As shown in Figure S6 (Supporting Information), strong cathodic peaks can be observed for the F-CP, BPC, and GF electrodes at ∼0.45 V, corresponding to the first discharge plateaus in the first discharge curves displayed in Figure 3a. These apparent peaks are originated from the electrolyte decomposition, leading to the formation of the SEI films on the surfaces of the carbonbased electrodes. Nevertheless, the intensity of the second cathodic peak of the F-CP electrode occurred at ∼0.02 V was much higher than that occurred for BPC or GF, in accordance with the longer second discharge plateau observed in Figure 3a. In the following discharge cycles, the cathodic peaks for the FCP, BPC, and GF electrode are almost completely overlapped (Supporting Information, Figure S6) due to the formation of stable SEI films during the first discharge cycle. During the charge process, however, the anodic peak at ∼0.13 V for F-CP became stable during the subsequent cycles (Supporting Information, Figure S6). Thus, the more highly reversible sodium ion insertion−extraction behavior for F-CP than BPC and GF indicate that the F-CP electrode has a higher sodium ion insertion/extraction capability than does the BPC or GF electrode. To evaluate the rate capability and cycling performance, we discharged and charged sodium-ion batteries on the basis of the F-CP, BPC, and GF electrodes for 80 cycles in the voltage range of 0.001−2.8 V from 0.05 to 10 A g−1. As illustrated in Figure 3b, the initial reversible capacities of the F-CP and BPC are 232 and 144 mA h g−1 under 50 mA g−1, which are approximately 7.7 and 4.8 times higher than that of GF (30 mA h g−1), respectively. Therefore, both the F-doping and large interlayer distance could greatly enhance the electrochemical performance of carbon materials. As expected, F-CP delivers much higher average charge capacities of 224 (0.05 A g−1), 242 (0.1 A g−1), 238 (0.2 A g−1), 207 (0.5 A g−1), 158 (1 A g−1), 102 (2 A g−1), 68 (5 A g−1), and 43 mA h g−1 (10 A g−1), than those of 132 (0.05 mA g−1), 115 (0.1 A g−1), 94 (0.2 A g−1), 75 (0.5 A g−1), 60 (1 A g−1), 45 (2 A g−1), 29 (5 A g−1), and 21 mA h g−1 (10 A g−1) for BPC, and 27 (0.05 A g−1), 23 (0.1 A g−1), 19 (0.2 A g−1), 15 (0.5 A g−1), 12 (1 A g−1), 10 (2 A g−1), 7.1 (5 A g−1), and 6.5 mA h g−1 (10 A g−1) for GF (Figure 3b). As displayed in Figure 3c, the charge capacity retention after 80 cycles at various current densities for F-CP (9.3%) is higher E


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with the previously reported carbonaceous materials (Supporting Information, Table S1).

4. CONCLUSIONS In summary, the electrochemical performance of F-doped carbon particles prepared by pyrolyzing of lotus petioles has been studied as anode materials for sodium-ion batteries. It was found that the F-CP electrode can deliver an initial charge capacity of 230 mA h g−1 at a current density of 50 mA g−1 between 0.001 and 2.8 V, significantly outperforms the corresponding value of 149 mA h g−1 for the banana peels derived counterpart. Even at 200 mA g−1, the F-CP electrode could still maintain a charge capacity of 228 mA h g−1 with initial charge capacity retention of 99.1% after 200 cycles compared to the BPC electrode with 107 mA h g−1 and 71.8%. The observed excellent performance of the F-CP electrode in sodium-ion batteries is attributed to synergistic effects associated with F-doping, enlarged interlayer distance, and disordered structure, to facilitate the diffusion of the large-size sodium ion, accommodate the effect of volume expansion during charge−discharge processes, and improve the storage of sodium ions. Such a long-life anode material with high rate capability and stable cyclic performance is promising for rechargeable Na-ion batteries.

Figure 4. (a) Ab initio simulation displaying the most stable configuration of F-CP. The black and green spheres represent C and F, respectively. (b) Nyquist plots of the F-CP cell before cycling and after 30, 100, and 200 cycles.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpcc.5b05443. Comparison of reported carbon-based anode materials for sodium-ion batteries; XPS analysis summary of F-CP;

significantly weakened. This offers a lower energy barrier for sodium ion insertion, more active reaction sites for sodium ion storage, and hence the capacity are excellent when compared

Figure 5. SEM and HRTEM images of the F-CP electrode material after 30 cycles (a, d), 100 cycles (b, e), and 200 cycles (c, f). Insets of parts d−f are the SAED patterns of the F-CP electrode material after 30, 100, and 200 cycles, respectively. F


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Solution for Enhanced Electrochemical Properties. J. Phys. Chem. C 2014, 118, 2970−2976. (10) Kim, D.; Lee, E.; Slater, M.; Lu, W.; Rood, S.; Johnson, C. S. Layered Na[Ni1/3Fe1/3Mn1/3]O2 Cathodes for Na-Ion Battery Application. Electrochem. Commun. 2012, 18, 66−69. (11) Sathiya, M.; Hemalatha, K.; Ramesha, K.; Tarascon, J.-M.; Prakash, A. S. Synthesis, Structure, and Electrochemical Properties of the Layered Sodium Insertion Cathode Material: NaNi1/3Mn1/3Co1/3O2. Chem. Mater. 2012, 24, 1846−1853. (12) Li, C.; Yin, C.; Mu, X.; Maier, J. Top-Down Synthesis of Open Framework Fluoride for Lithium and Sodium Batteries. Chem. Mater. 2013, 25, 962−969. (13) 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. (14) Lee, K. T.; Ramesh, T. N.; Nan, F.; Botton, G.; Nazar, L. F. Topochemical Synthesis of Sodium Metal Phosphate Olivines for Sodium-Ion Batteries. Chem. Mater. 2011, 23, 3593−3600. (15) Ellis, B. L.; Makahnouk, W. R. M.; Makimura, Y.; Toghill, K.; Nazar, L. F. A Multifunctional 3.5 V Iron-Based Phosphate Cathode for Rechargeable Batteries. Nat. Mater. 2007, 6, 749−753. (16) Barpanda, P.; Liu, G.; Ling, C. D.; Tamaru, M.; Avdeev, M.; Chung, S.-C.; Yamada, Y.; Yamada, A. Na2FeP2O7: A Safe Cathode for Rechargeable Sodium-ion Batteries. Chem. Mater. 2013, 25, 3480− 3487. (17) Li, S.; Dong, Y.; Xu, L.; Xu, X.; He, L.; Mai, L. Effect of Carbon Matrix Dimensions on the Electrochemical Properties of Na3V2(PO4)3 Nanograins for High-Performance Symmetric Sodium-Ion Batteries. Adv. Mater. 2014, 26, 3545−3553. (18) Zhu, C.; Song, K.; van Aken, P. A.; Maier, J.; Yu, Y. CarbonCoated Na3V2(PO4)3 Embedded in Porous Carbon Matrix: An Ultrafast Na-Storage Cathode with the Potential of Outperforming Li Cathodes. Nano Lett. 2014, 14, 2175−2180. (19) Yuan, D.; Liang, X.; Wu, L.; Cao, Y.; Ai, X.; Feng, J.; Yang, H. A Honeycomb-Layered Na3Ni2SbO6: A High-Rate and Cycle-Stable Cathode for Sodium-Ion Batteries. Adv. Mater. 2014, 26, 6301−6306. (20) You, Y.; Wu, X.-L.; Yin, Y.-X.; Guo, Y.-G. High-Quality Prussian blue Crystals as Superior Cathode Materials for Room-Temperature Sodium-Ion Batteries. Energy Environ. Sci. 2014, 7, 1643−1647. (21) Song, J.; Wang, L.; Lu, Y.; Liu, J.; Guo, B.; Xiao, P.; Lee, J.-J.; Yang, X.-Q.; Henkelman, G.; Goodenough, J. B. Removal of Interstitial H2O in Hexacyanometallates for a Superior Cathode of a Sodium-Ion Battery. J. Am. Chem. Soc. 2015, 137, 2658−2664. (22) Pan, H.; Lu, X.; Yu, X.; Hu, Y.-S.; Li, H.; Yang, X.-Q.; Chen, L. Sodium Storage and Transport Properties in Layered Na2Ti3O7 for Room-Temperature Sodium-Ion Batteries. Adv. Energy Mater. 2013, 3, 1186−1194. (23) Sun, Y.; Zhao, L.; Pan, H.; Lu, X.; Gu, L.; Hu, Y.-S.; Li, H.; Armand, M.; Ikuhara, Y.; Chen, L.; Huang, X. Direct Atomic-Scale Confirmation of Three-Phase Storage Mechanism in Li4Ti5O12 Anodes for Room-Temperature Sodium-Ion Batteries. Nat. Commun. 2013, 4, 1870. (24) Hu, Z.; Wang, L.; Zhang, K.; Wang, J.; Cheng, F.; Tao, Z.; Chen, J. MoS2 Nanoflowers with Expanded Interlayers as HighPerformance Anode for Sodium-Ion Batteries. Angew. Chem., Int. Ed. 2014, 53, 12794−12798. (25) Zhu, H.; Jia, Z.; Chen, Y.; Weadock, N.; Wan, J.; Vaaland, O.; Han, X.; Li, T.; Hu, L. Tin Anode for Sodium-Ion Batteries Using Natural Wood Fiber as a Mechanical Buffer and Electrolyte Reservoir. Nano Lett. 2013, 13, 3093−3100. (26) Qian, J.; Chen, Y.; Wu, L.; Cao, Y.; Ai, X.; Yang, H. High Capacity Na-Storage and Superior Cyclability of Nanocomposite Sb/C Anode for Na-Ion Batteries. Chem. Commun. 2012, 48, 7070−7072. (27) Zhou, X.; Liu, X.; Xu, Y.; Liu, Y.; Dai, Z.; Bao, J. An SbOx/ Reduced Graphene Oxide Composite as a High-Rate Anode Material for Sodium-Ion Batteries. J. Phys. Chem. C 2014, 118, 23527−23534. (28) Song, J.; Yu, Z.; Gordin, M. L.; Hu, S.; Yi, R.; Tang, D.; Walter, T.; Regula, M.; Choi, D.; Li, X.; Manivannan, A.; Wang, D. Chemically

photographs of the completely dehydrated lotus petioles and F-CP; nitrogen adsorption−desorption isotherms of F-CP and BPC; SIMS spectra of GF, BPC and F-CP; C 1s XPS spectrum of F-CP; thermal analysis (TG-DSC) curves of GF, BPC, and F-CP; CV curves of the first three cycles of the GF, BPC, and F-CP electrodes; Coulombic efficiencies of the GF, BPC, and F-CP electrodes; galvanostatic charge−discharge profiles of the initial five cycles for the F-CP electrode; and cycling performance and Coulombic efficiency of the F-CP electrode, where the first 5 cycles are under 50 mA g−1 and the remaining 295 cycles are under 500 mA g−1. (PDF)

AUTHOR INFORMATION


Corresponding Authors

*(X.Z.) E-mail: [email protected]. Telephone/Fax: +8625-85891027. *(Z.D.) E-mail: [email protected]. Telephone/Fax: +8625-85891051. Author Contributions †

P.W. and B.Q. contributed equally to this work.

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), the Natural Science Foundation of Jiangsu Province of China (BK20140915), the Scientific Research Foundation for Advanced Talents of Nanjing Normal University (2014103XGQ0073), the financial support from the Priority Academic Program Development of Jiangsu Higher Education Institutions, and the Program of Jiangsu Collaborative Innovation Center of Biomedical Functional Materials.

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REFERENCES

(1) Goodenough, J. B.; Park, K.-S. The Li-Ion Rechargeable Battery: A Perspective. J. Am. Chem. Soc. 2013, 135, 1167−1176. (2) Tarascon, J.-M. Is Lithium the New Gold? Nat. Chem. 2010, 2, 510−510. (3) 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. (4) Pan, H.; Hu, Y.-S.; Chen, L. Room-Temperature Stationary Sodium-Ion Batteries for Large-Scale Electric Energy Storage. Energy Environ. Sci. 2013, 6, 2338−2360. (5) 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. (6) Slater, M. D.; Kim, D.; Lee, E.; Johnson, C. S. Sodium-Ion Batteries. Adv. Funct. Mater. 2013, 23, 947−958. (7) D’Arienzo, M.; Ruffo, R.; Scotti, R.; Morazzoni, F.; Mari, C. M.; Polizzi, S. Layered Na0.71CoO2: A Powerful Candidate for Viable and High Performance Na-Batteries. Phys. Chem. Chem. Phys. 2012, 14, 5945−5952. (8) Yabuuchi, N.; Kajiyama, M.; Iwatate, J.; Nishikawa, H.; Hitomi, S.; Okuyama, R.; Usui, R.; Yamada, Y.; Komaba, S. P2-Type Nax[Fe1/2Mn1/2]O2 Made from Earth-Abundant Elements for Rechargeable Na Batteries. Nat. Mater. 2012, 11, 512−517. (9) Wang, X.; Liu, G.; Iwao, T.; Okubo, M.; Yamada, A. Role of Ligand-to-Metal Charge Transfer in O3-Type NaFeO2−NaNiO2 Solid G


Article


The Journal of Physical Chemistry C Bonded Phosphorus/Graphene Hybrid as a HighPerformance Anode for Sodium-Ion Batteries. Nano Lett. 2014, 14, 6329−6335. (29) Zhu, Y.; Wen, Y.; Fan, X.; Gao, T.; Han, F.; Luo, C.; Liou, S.-C.; Wang, C. Red Phosphorus−Single-Walled Carbon Nanotube Composite as a Superior Anode for Sodium Ion Batteries. ACS Nano 2015, 9, 3254−3264. (30) Wang, H.; Hu, P.; Yang, J.; Gong, G.; Guo, L.; Chen, X. Renewable-Juglone-Based High-Performance Sodium-Ion Batteries. Adv. Mater. 2015, 27, 2348−2354. (31) Ge, P.; Fouletier, M. Electrochemical Intercalation of Sodium in Graphite. Solid State Ionics 1988, 28−30, 1172−1175. (32) Stevens, D. A.; Dahn, J. R. The Mechanisms of Lithium and Sodium Insertion in Carbon Materials. J. Electrochem. Soc. 2001, 148, A803−A811. (33) Thomas, P.; Billaud, D. Electrochemical Insertion of Sodium into Hard Carbons. Electrochim. Acta 2002, 47, 3303−3307. (34) Komaba, S.; Murata, W.; Ishikawa, T.; Yabuuchi, N.; Ozeki, T.; Nakayama, T.; Ogata, A.; Gotoh, K.; Fujiwara, K. Electrochemical Na Insertion and Solid Electrolyte Interphase for Hard-Carbon Electrodes and Application to Na-Ion Batteries. Adv. Funct. Mater. 2011, 21, 3859−3867. (35) Ponrouch, A.; Goñi, A. R.; Palacín, M. R. High Capacity Hard Carbon Anodes for Sodium Ion Batteries in Additive Free Electrolyte. Electrochem. Commun. 2013, 27, 85−88. (36) Babu, R. S.; Pyo, M. Hard Carbon and Carbon Nanotube Composites for the Improvement of Low-Voltage Performance in Na Ion Batteries. J. Electrochem. Soc. 2014, 161, A1045−A1050. (37) Fukunaga, A.; Nohira, T.; Hagiwara, R.; Numata, K.; Itani, E.; Sakai, S.; Nitta, K.; Inazawa, S. A Safe and High-Rate Negative Electrode for Sodium-Ion Batteries: Hard Carbon in NaFSAC1C3pyrFSA Ionic Liquid at 363 K. J. Power Sources 2014, 246, 387−391. (38) Bommier, C.; Luo, W.; Gao, W.-Y.; Greaney, A.; Ma, S.; Ji, X. Predicting Capacity of Hard Carbon Anodes in Sodium-Ion Batteries Using Porosity Measurements. Carbon 2014, 76, 165−174. (39) Zhou, X.; Zhu, X.; Liu, X.; Xu, Y.; Liu, Y.; Dai, Z.; Bao, J. Ultralong Cycle Life Sodium-Ion Battery Anodes Using a GrapheneTemplated Carbon Hybrid. J. Phys. Chem. C 2014, 118, 22426−22431. (40) Hong, K.-L.; Qie, L.; Zeng, R.; Yi, Z.-Q.; Zhang, W.; Wang, D.; Yin, W.; Wu, C.; Fan, Q.-J.; Zhang, W.-X.; Huang, Y.-H. Biomass Derived Hard Carbon Used as a High Performance Anode Material for Sodium Ion Batteries. J. Mater. Chem. A 2014, 2, 12733−12738. (41) Li, Y.; Xu, S.; Wu, X.; Yu, J.; Wang, Y.; Hu, Y.-S.; Li, H.; Chen, L.; Huang, X. Amorphous Monodispersed Hard Carbon MicroSpherules Derived from Biomass as a High Performance Negative Electrode Material for Sodium-Ion Batteries. J. Mater. Chem. A 2015, 3, 71−77. (42) Luo, W.; Bommier, C.; Jian, Z.; Li, X.; Carter, R.; Vail, S.; Lu, Y.; Lee, J.-J.; Ji, X. Low-Surface-Area Hard Carbon Anode for Na-Ion Batteries via Graphene Oxide as a Dehydration Agent. ACS Appl. Mater. Interfaces 2015, 7, 2626−2631. (43) Bai, Y.; Wang, Z.; Wu, C.; Xu, R.; Wu, F.; Liu, Y.; Li, H.; Li, Y.; Lu, J.; Amine, K. Hard Carbon Originated from Polyvinyl Chloride Nanofibers As High-Performance Anode Material for Na-Ion Battery. ACS Appl. Mater. Interfaces 2015, 7, 5598−5604. (44) Alcántara, R.; Jiménez-Mateos, J. M.; Lavela, P.; Tirado, J. L. Carbon Black: A Promising Electrode Material for Sodium-Ion Batteries. Electrochem. Commun. 2001, 3, 639−642. (45) Alcántara, R.; Jiménez-Mateos, J. M.; Tirado, J. L. Negative Electrodes for Lithium-and Sodium-Ion Batteries Obtained by HeatTreatment of Petroleum Cokes below 1000 °C. J. Electrochem. Soc. 2002, 149, A201−A205. (46) Cao, Y.; Xiao, L.; Sushko, M. L.; Wang, W.; Schwenzer, B.; Xiao, J.; Nie, Z.; Saraf, L. V.; Yang, Z.; Liu, J. Sodium Ion Insertion in Hollow Carbon Nanowires for Battery Applications. Nano Lett. 2012, 12, 3783−3787. (47) Wang, Z.; Qie, L.; Yuan, L.; Zhang, W.; Hu, X.; Huang, Y. Functionalized N-doped Interconnected Carbon Nanofibers as an

Anode Material for Sodium-Ion Storage with Excellent Performance. Carbon 2013, 55, 328−334. (48) Wang, Y.-X.; Chou, S.-L.; Liu, H.-K.; Dou, S.-X. Reduced Graphene Oxide with Superior Cycling Stability and Rate Capability for Sodium Storage. Carbon 2013, 57, 202−208. (49) David, L.; Singh, G. Reduced Graphene Oxide Paper Electrode: Opposing Effect of Thermal Annealing on Li and Na Cyclability. J. Phys. Chem. C 2014, 118, 28401−28408. (50) Yan, Y.; Yin, Y.-X.; Guo, Y.-G.; Wan, L.-J. A Sandwich-Like Hierarchically Porous Carbon/Graphene Composite as a HighPerformance Anode Material for Sodium-Ion Batteries. Adv. Energy Mater. 2014, 4, 1301584. (51) Wang, H.-G.; Wu, Z.; Meng, F.-L.; Ma, D.-L.; Huang, X.-L.; Wang, L.-M.; Zhang, X.-B. Nitrogen-Doped Porous Carbon Nanosheets as Low-Cost, High-Performance Anode Material for SodiumIon Batteries. ChemSusChem 2013, 6, 56−60. (52) Lotfabad, E. M.; Ding, J.; Cui, K.; Kohandehghan, A.; Kalisvaart, W. P.; Hazelton, M.; Mitlin, D. High-Density Sodium and Lithium Ion Battery Anodes from Banana Peels. ACS Nano 2014, 8, 7115−7129. (53) Xu, J.; Wang, M.; Wickramaratne, N. P.; Jaroniec, M.; Dou, S.; Dai, L. High-Performance Sodium Ion Batteries Based on a 3D Anode from Nitrogen-Doped Graphene Foams. Adv. Mater. 2015, 27, 2042− 2048. (54) Wenzel, S.; Hara, T.; Janek, J.; Adelhelm, P. Room-Temperature Sodium-Ion Batteries: Improving the Rate Capability of Carbon Anode Materials by Templating Strategies. Energy Environ. Sci. 2011, 4, 3342−3345. (55) Fu, L.; Tang, K.; Song, K.; van Aken, P. A.; Yu, Y.; Maier, J. Nitrogen Doped Carbon Fibres as Anode Materials for Sodium Ion Batteries with Excellent Rate Performance. Nanoscale 2014, 6, 1384− 1389. (56) Pol, V. G.; Lee, E.; Zhou, D.; Dogan, F.; Calderon-Moreno, J. M.; Johnson, C. S. Spherical Carbon as a New High-Rate Anode for Sodium-Ion Batteries. Electrochim. Acta 2014, 127, 61−67. (57) Chen, T.; Pan, L.; Lu, T.; Fu, C.; Chua, D. H. C.; Sun, Z. Fast Synthesis of Carbon Microspheres via a Microwave-Assisted Reaction for Sodium Ion Batteries. J. Mater. Chem. A 2014, 2, 1263−1267. (58) Chen, T.; Liu, Y.; Pan, L.; Lu, T.; Yao, Y.; Sun, Z.; Chua, D. H. C.; Chen, Q. Electrospun Carbon Nanofibers as Anode Materials for Sodium Ion Batteries with Excellent Cycle Performance. J. Mater. Chem. A 2014, 2, 4117−4121. (59) Song, H.; Li, N.; Cui, H.; Wang, C. Enhanced Storage Capability and Kinetic Processes by Pores-and Hetero-Atoms-Riched Carbon Nanobubbles for Lithium-Ion and Sodium-Ion Batteries Anodes. Nano Energy 2014, 4, 81−87. (60) Li, W.; Zeng, L.; Yang, Z.; Gu, L.; Wang, J.; Liu, X.; Cheng, J.; Yu, Y. Free-Standing and Binder-Free Sodium-Ion Electrodes with Ultralong Cycle Life and High Rate Performance Based on Porous Carbon Nanofibers. Nanoscale 2014, 6, 693−698. (61) Liu, Y.; Fan, F.; Wang, J.; Liu, Y.; Chen, H.; Jungjohann, K. L.; Xu, Y.; Zhu, Y.; Bigio, D.; Zhu, T.; Wang, C. In Situ Transmission Electron Microscopy Study of Electrochemical Sodiation and Potassiation of Carbon Nanofibers. Nano Lett. 2014, 14, 3445−3452. (62) Jin, J.; Shi, Z.-Q.; Wang, C.-Y. Electrochemical Performance of Electrospun carbon nanofibers as free-standing and binder-free anodes for Sodium-Ion and Lithium-Ion Batteries. Electrochim. Acta 2014, 141, 302−310. (63) Matsuo, Y.; Ueda, K. Pyrolytic Carbon from Graphite Oxide as a Negative Electrode of Sodium-Ion Battery. J. Power Sources 2014, 263, 158−162. (64) Suryawanshi, A.; Mhamane, D.; Nagane, S.; Patil, S.; Aravindan, V.; Ogale, S.; Srinivasan, M. Indanthrone Derived Disordered Graphitic Carbon as Promising Insertion Anode for Sodium Ion Battery with Long Cycle Life. Electrochim. Acta 2014, 146, 218−223. (65) Jin, J.; Yu, B.-J.; Shi, Z.-Q.; Wang, C.-Y.; Chong, C.-B. LigninBased Electrospun Carbon Nanofibrous Webs as Free-Standing and Binder-Free Electrodes for Sodium Ion Batteries. J. Power Sources 2014, 272, 800−807. H


Article


The Journal of Physical Chemistry C (66) Ding, J.; Wang, H.; Li, Z.; Cui, K.; Karpuzov, D.; Tan, X.; Kohandehghan, A.; Mitlin, D. Peanut Shell Hybrid Sodium Ion Capacitor with Extreme Energy−Power Rivals Lithium Ion Capacitors. Energy Environ. Sci. 2015, 8, 941−955. (67) Kim, H.; Hong, J.; Park, Y.-U.; Kim, J.; Hwang, I.; Kang, K. Sodium Storage Behavior in Natural Graphite using Ether-based Electrolyte Systems. Adv. Funct. Mater. 2015, 25, 534−541. (68) Zhang, K.; Li, X.; Liang, J.; Zhu, Y.; Hu, L.; Cheng, Q.; Guo, C.; Lin, N.; Qian, Y. Nitrogen-Doped Porous Interconnected DoubleShelled Hollow Carbon Spheres with High Capacity for Lithium Ion Batteries and Sodium Ion Batteries. Electrochim. Acta 2015, 155, 174− 182. (69) Yun, Y. S.; Cho, S. Y.; Kim, H.; Jin, H.-J.; Kang, K. Ultra-Thin Hollow Carbon Nanospheres for Pseudocapacitive Sodium-Ion Storage. ChemElectroChem 2015, 2, 359−365. (70) Tang, K.; Fu, L.; White, R. J.; Yu, L.; Titirici, M. M.; Antonietti, M.; Maier, J. Hollow Carbon Nanospheres with Superior Rate Capability for Sodium-Based Batteries. Adv. Energy Mater. 2012, 2, 873−877. (71) Luo, W.; Schardt, J.; Bommier, C.; Wang, B.; Razink, J.; Simonsen, J.; Ji, X. Carbon Nanofibers Derived from Cellulose Nanofibers as a Long-Life Anode Material for Rechargeable SodiumIon Batteries. J. Mater. Chem. A 2013, 1, 10662−10666. (72) Ding, J.; Wang, H.; Li, Z.; Kohandehghan, A.; Cui, K.; Xu, Z.; Zahiri, B.; Tan, X.; Lotfabad, E. M.; Olsen, B. C.; Mitlin, D. Carbon Nanosheet Frameworks Derived from Peat Moss as High Performance Sodium Ion Battery Anodes. ACS Nano 2013, 7, 11004−11015. (73) Zhou, X.; Guo, Y.-G. Highly Disordered Carbon as a Superior Anode Material for Room-Temperature Sodium-Ion Batteries. ChemElectroChem 2014, 1, 83−86. (74) Wen, Y.; He, K.; Zhu, Y.; Han, F.; Xu, Y.; Matsuda, I.; Ishii, Y.; Cumings, J.; Wang, C. Expanded Graphite as Superior Anode for Sodium-Ion Batteries. Nat. Commun. 2014, 5, 4033. (75) Paraknowitsch, J. P.; Thomas, A. Doping Carbons beyond Nitrogen: An Overview of Advanced Heteroatom Doped Carbons with Boron, Sulphur and Phosphorus for Energy Applications. Energy Environ. Sci. 2013, 6, 2839−2855. (76) Xu, J.; Jeon, I.-Y.; Seo, J.-M.; Dou, S.; Dai, L.; Baek, J.-B. EdgeSelectively Halogenated Graphene Nanoplatelets (XGnPs, X = Cl, Br, or I) Prepared by Ball-Milling and Used as Anode Materials for Lithium-Ion Batteries. Adv. Mater. 2014, 26, 7317−7323. (77) Delley, B. An All-electron Numerical Method for Solving the Local Density Functional for Polyatomic Molecules. J. Chem. Phys. 1990, 92, 508−517. (78) Delley, B. From Molecules to Solids with the DMol3 Approach. J. Chem. Phys. 2000, 113, 7756−7764. (79) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865−3868. (80) Grimme, S. Semiempirical GGA-Type Density Functional Constructed with a Long-Rang Dispersion Correction. J. Comput. Chem. 2006, 27, 1787−1799. (81) Zhao, F.-G.; Zhao, G.; Liu, X.-H.; Ge, C.-W.; Wang, J.-T.; Li, B.L.; Wang, Q.-G.; Li, W.-S.; Chen, Q.-Y. Fluorinated Graphene: Facile Solution Preparation and Tailorable Properties by Fluorine-Content Tuning. J. Mater. Chem. A 2014, 2, 8782−8789.

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Fluorine-Doped Carbon Particles Derived from Lotus Petioles as High

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