C Hollow Nanosphere Hybrid for High-Capacity and

Oct 12, 2017 - Herein, an urchin-like V2O3/C hybrid composed of 1D nanofibers (a length-to-diameter ratio of 4) and hollow nanospheres (a diameter of ...
7 downloads 0 Views 5MB Size
Download PDF
Research Article pubs.acs.org/journal/ascecg

Urchin-like V2O3/C Hollow Nanosphere Hybrid for High-Capacity and Long-Cycle-Life Lithium Storage Peng Yu, Xu Liu, Lei Wang,* Chungui Tian, Haitao Yu, and Honggang Fu* Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People’s Republic of China, Heilongjiang University, Xuefu Road, Harbin 150080, People’s Republic of China S Supporting Information *

ABSTRACT: Vanadium oxides (VOx) show potential in Li-ion batteries (LIBs) originating from their abundance, low cost, and high theoretical capacities. Although V2O3 exhibits a high theoretical capacity of 1070 mAh g−1, most of the current reported for V2O3-based anodes suffer from poor electrical conductivity and huge volume change upon cycling in practice. Herein, an urchin-like V2O3/C hybrid composed of 1D nanofibers (a length-to-diameter ratio of 4) and hollow nanospheres (a diameter of 200−300 nm) has been synthesized via a template-free solvothermal method combined with a carbothermal reduction strategy. Both the nanofibers and hollow nanospheres consist of carbon-coated V2O3 nanostructures. During the solvothermal process, glucose plays not only as the carbon resource but also as the structural direction agent of nanosphere structures, and the formation of 1D V2O3 nanofibers is attributed to the epitaxial growth of V2O3 nanoparticles on the outer surface of nanosheets. When applied as an LIB anode, the hybrid could exhibit an ultrahigh reversible capacity of 1250 mAh g−1 at 1 A g−1 after 1000 cycles, and a capacity of 500 mAh g−1 still could be achieved even at 500 mA g−1. Moreover, the V2O3/C hybrid anode can match well with the commercial high-voltage LiMn1/3Co1/3Ni1/3O2 cathode for fabricating a full cell with a specific capacity of 197.2 mAh g−1 between 2.0 and 4.7 V at 100 mA g−1, and a high energy density of ca. 740 Wh kg−1 at a power rate of 375 W kg−1, which is sufficient to turn on a 3 V and 10 mW LED. KEYWORDS: Urchin-like structure, Hollow sphere, Vanadium oxides, Anode, Li-ion battery

■

anodes.14−17 Particularly, V2O3 could experience an intriguing change from insulator to metal as a function of temperature.18 In detail, it shows a relatively lower electrical resistance at the normal operating temperature of LIBs (253−333 K) compared with other transition metal oxides, such as Fe2O3, Co3O4, MnO2, etc., which endows V2O3 with a fascinating rate capability in theory.19−22 This is attributed to the metallic behavior resulting from the 3D V−V framework in V2O3 making V3 electrons able to tour along the V−V chains. Additionally, the high theoretical capacity of 1070 mAh g−1 makes V2O3 an ideal electrode material for advanced LIBs.23 However, most currently reported V2O3-based anodes are far from satisfactory. Like most transitional metal oxides, V2O3 anodes also face the problems of poor cyclic stability and rate performance, which are mainly attributed to intrinsically insufficient electron conductive ability and inevitable tremendous volume variation during Li+ insertion/extraction.24,25 To cover the above shortages, considerable research has been devoted to exploring hybrid nanostructures composed of inorganic nanostructures (nanospheres, nanotubes, nanofibers, nanosheets, etc.) and carbon-based species (amorphous carbon,

INTRODUCTION To impel the applications of portable electronic devices, hybrid electrical vehicles, and electrical grids, the exploitation of advanced energy storage devices as a predominant power source is an essential prerequisite.1,2 Lithium ion batteries (LIBs) are the prior choice because of their excellent energy density and power density, good safety, and long lifespan. It is well-known that the electrode materials play a decisive role in the performance of LIBs.3 However, the relatively low theoretical capacity (372 mAh g−1) and poor rate capability of graphite anodes cannot meet the ever-increasing demand for next-generation LIBs.4,5 In contrast, the high-capacity Si-based electrodes show limited cycling performance owing to the huge volume variation during the lithium insertion/extraction.6,7 In the past few years, tremendous efforts have been devoted to developing novel advanced substituted electrode materials.8−10 Vanadium oxides (VOx), a kind of earth-abundant and inexpensive transition-metal oxide, have been extensively researched as promising candidates for LIB anodes.11−13 Owing to vanadium possessing several different stable oxidation states (+3, +4, and +5), many oxides, such as V2O5, VO2, V2O3, VOOH, and so forth, have been explored as LIB electrodes. Among them, V2O5 and VO2 with a high valence of V are applied as cathode materials because of their high intercalation voltage, while the low valence VOx’s are more suitable as © 2017 American Chemical Society

Received: May 25, 2017 Revised: September 25, 2017 Published: October 12, 2017 11238

DOI: 10.1021/acssuschemeng.7b01640 ACS Sustainable Chem. Eng. 2017, 5, 11238−11245

Research Article

ACS Sustainable Chemistry & Engineering

(1253.6 eV). The N2 adsorption/desorption isotherms were collected on Micromeritics Tristar II. The samples were outgassed for 10 h at 150 °C under a vacuum before the measurements. The X-ray absorption spectroscopy data were collected on Beamline BL14W1 at the Shanghai Synchrotron Radiation Facility (SSRF) through transmission mode, using a Si (111) double crystal monochromator for energy selection. Meanwhile, the XAFS data for V2O3, VO2, and V2O5 were measured for comparison. Electrochemical Measurements. To investigate the electrochemical performance, working electrodes were prepared via pasting the mixture containing active materials, super-P carbon black, and polyvinylidene fluorides (PVDF) with a weight ratio of 8:1:1 onto copper foil using N-methyl-2-pyrrolidinone (NMP) as a solvent. After drying in a vacuum at 100 °C for 10 h, the electrode was punched into a round shape with a diameter of 14 mm. The active material loading was about 1.2−1.5 mg cm−2. For half cells, CR2025 coin-type cells were assembled in an Ar filled glovebox using lithium metal as the counter/reference electrode, a Cellgard 2400 membrane as the separator, and 1 M LiPF6 into 1:1:1 EC/EMC/DMC organic solutions as the electrolyte. Charge−discharge profiles for the half cells were recorded using a LAND CT2001A system (Wuhan Jinnuo Electronics, Ltd.). Cyclic voltammetry was performed on an Autolab (Metrohm, Switzerland) at a scanning rate of 0.1 mV s−1 with a range from 0.01 to 3.0 V. Electrochemical impedance spectroscopy (EIS) was carried out on an Autolab with a frequency in the range of 10 kHz to 10 MHz with an AC signal of 5 mV in amplitude as the perturbation. For further investigation, cycled batteries were disassembled in the argon-filled glovebox with the obtained electrode washed with dimethyl carbonate (DMC) and ethanol mixed solvent to remove the residual salts and electrolytes on the surface. For full cell assembly, the LiMn1/3Co1/3Ni1/3O2 electrode was employed as the cathode material (charge and discharge profile of the LiMn1/3Co1/3Ni1/3O2 electrode shown in Figure S18) with a loading mass of 1.0−1.2 mg cm−2; LiMn1/3Co1/3Ni1/3O2 and its charge− discharge cycles were evaluated at 1.0 A g−1 in voltage windows between 2.0 and 4.5 V. All the specific capacities and current densities were calculated by the total weight of the nanocomposite.

carbon spheres, carbon nanotubes, graphene, etc.) for LIB anodes.26,27 For instance, peapod-like V2O3 nanorods encapsulated into carbon nanostructures were prepared via a multistep hydrothermal route to reduce V2O5, which exhibit appreciable rate capability and desired long-term cycling stability.28 As such, carbon-supported nanosheet-assembled VOx microspheres synthesized via a solvothermal reaction could deliver high-rate and long-life performance with a specific capacity of 860 mAh g−1 at 1000 mA g−1.23 It is well demonstrated that these hybrid constructions could improve the electronic conductivity and the overall structural stability. Moreover, hollow nanostructures could effectively accommodate the volume changes of conversion reaction V2O3 + xLi+ + xe− = LixV2O3 during cycling to induce a large capacitance and excellent stability performance.29 Despite the progress, there are rare reports about the designed synthesis of V2O3@C hollow nanospheres due to the limitations of present synthetic strategies. Herein, a novel hybrid of urchin-like V2O3/C hollow nanospheres is reported by combining a template-free solvothermal and carbothermal reduction strategy. During the solvothermal process, metavanadate was coordinated with glucose uniformly and then formed nanospheres precursor under the structural direction effect of glucose. Afterward, the precursor was gradually decomposed to hollow nanospheres, accompanied by the epitaxial growth of V2O3 nanoparticles to form 1D nanofibers, so urchin-like V2O3/C hollow nanospheres could be obtained. The special hybrid offers many remarkable advantages, including the hollow nanosphere structures being able to provide more space to accommodate the huge volume change during the insertion and extraction of Li ions; the intimate contact between V2O3 and amorphous carbon could shorten the diffusion pathway of Li+ ions and electrons. As a result, the hybrid shows high reversible capacity, outstanding stability, and extraordinary rate capability when applied as an LIB anode. The full cell assembled by using V2O3/C as a cathode together with commercial LiMn1/3Co1/3Ni1/3O2 as a cathode displays high capacity, high energy, and power density.

■

■

RESULTS AND DISCUSSION The morphology of the V2O3/C and its precursor are presented in Figure 1. According to the SEM image in Figure 1a, the

EXPERIMENTAL SECTION

Synthesis of V2O3/C Composites. For V2O3/C, 1 mmol of ammonium metavanadate was dissolved in 20 mL of ethanol and and 1 mmol of glucose in 15 mL of distilled water. Then the above two solutions were mixed and magnetically stirred to form a homogeneous light-yellow solution. Afterward, the above solution was transferred into a Teflon-lined autoclave and then maintained at 180 °C for 24 h. After that, the resultant black precipitant was obtained by centrifugation and then washed with deionized water and ethanol several times. Subsequently the obtained product was dried at 80 °C overnight. Finally, the resultant black-green solid was heated under a N2 atmosphere with a heating rate of 5 °C/min and then maintained at 700 °C for 2 h, leading to the formation of V2O3/C composites. For comparison, VOx rods were synthesized through similar processes without glucose; carbon spheres were synthesized without ammonium metavanadate. Characterizations. The X-ray diffraction (XRD) patterns were collected by a Bruker D8 Advance diffractometer equipped with Cu Kα (λ = 1.5406 Å) radiation in the range 10−80°. Raman spectra were recorded with a Jobin Yvon HR 800 micro-Raman spectrometer at 457.9 nm. Thermogravimetric analyses (TGA) were carried out with a TA Q600 in air. Scanning electron microscopy (SEM) images were recorded with a Hitachi S-4800 field emission scanning electron microscope operating at 15 kV. Transmission electron microscopy (TEM) images were recorded on a JEM-2100 electron microscope (JEOL, Japan, acceleration 200 kV). XPS analyses were performed on a VG ESCALABMK II device with a Mg Ka achromatic X-ray source

Figure 1. (a) SEM and (b,c) TEM images of the V2O3/C precursor. (d) SEM, (e) TEM, and (f) HRTEM images of V2O3/C (inset, SAED pattern).

precursor synthesized from the solvothermal process possess a uniformly spherical shape with a diameter in the range of 200− 300 nm. TEM and HRTEM images (Figure 1b and c) indicate that the spherical structures are solid and the surface is smooth. The element mapping of the V2O3/C precursor were shown in Figure S1, showing that the V, O, C, and N are evenly distribute in the spherical precursor. On the opposite, the uniform sphere structures with a rough surface are obtained after decomposing 11239

DOI: 10.1021/acssuschemeng.7b01640 ACS Sustainable Chem. Eng. 2017, 5, 11238−11245

Research Article

ACS Sustainable Chemistry & Engineering

Figure 2. (a) XRD patterns of the V2O3/C hybrid. (b) Raman spectra of as synthesized V2O3/C composites. (c) High-resolution V2p XPS spectrum of the V2O3/C hybrid. (d) V K-edge XANES of V2O3/C hybrid, and corresponding references V2O3, VO2, and V2O5.

cm−1 can be ascribed to the disordered carbon (D band) and the graphitic carbon (G band), which confirms the existence of a carbon component. Thermogravimetric (TG) analysis in Figure S7 indicates that the carbon content in V2O3/C hollow nanospheres is about 16.9%. The EDX spectrum (shown in Figure S8) shows that the atom percentages of V, C, and O in the V2O3/C hybrid are about 21.8, 40.1, and 38.1%, respectively, implying that more of the carbon component distributes on the periphery of the nanostructure. X-ray photoelectron spectroscopy is applied for further investigation of element valence states. As shown in Figure S9, typical peaks of C1s, V2p, V3s, V3p, and O1s for the V2O3/C hybrid can be detected in the XPS wide spectrum. Figure 2c shows the highresolution V2p XPS spectrum of the V2O3/C hybrid, the two peaks at 516.1 and 523.5 eV attributed to V2p 3/2 and V2p 1/2 from V3+, respectively. In order to further verify the valence of V in the V2O3/C hybrid, a XANES analysis was performed using VO2 (IV), V2O3(III), and V2O5(V) as the standards. As exhibited in Figure 2d, the pre-edge features of V can be observed at around 5470 eV in all V-based oxide. Moreover, it can be observed that, with the increase of oxidation state in VO x , the absorb peak shifted slightly toward higher energies.30,31 The valence state of V in V2O3/C is closer to +3, which is consistent with the result from the XPS analysis. Investigation of the formation mechanism of the nanostructure has guiding significance for directional synthesis of nanomaterials with special structures.32 For exploring the formation processes of the V2O3/C hollow nanospheres, the solvothermal time was first studied for researching the formation process of sphere structures. The corresponding XRD patterns in Figure S10 reveal the amorphous characteristics of the precursor derived from different solvothermal times. FT-IR spectra of the precursor at different solvothermal reaction times and the V2O3/C hybrid are shown in Figure S11. For the precursor, the peaks located at about 2918 cm−1 are related to the stretching vibrations of −CH3 groups and the peak at 2850 cm−1 is related to the −CH2− groups. After thermal treatment, both of them disappeared due to the

the precursor, as can be seen from Figure 1d. It is further illustrated that the V2O3/C nanospheres were homogeneous and uniformly dispersed as exhibited in Figure S2. The TEM image reveals that the V2O3/C nanospheres have a hollow interior with a shell thickness of 30−40 nm (Figure 1e and Figure S3). The surface of the nanospheres is scattered around by lots of nanothorns, with a diameter of about 10 nm and a length of about 35−45 nm, the length−diameter ratio of the nanothorns is approximately 4. The electron diffraction (SAED) pattern is shown in Figure 1f. The interplanar spacing of 0.46 nm coincides with the (116) facets of rhombohedral V2O3, consistent with previous reports.23,24,28 Moreover, the skeleton of the shell was composed of V2O3 and amorphous carbon. Additionally, VOx rods with a 500 nm thickness and 5−10 μm length instead of sphere nanostructures were formed in the absence of ammonium metavanadate (Figure S4). Also, it should be noted that carbonaceous spheres were obtained through the solvothermal reaction of glucose (Figure S5), indicating that glucose is served as the structural direction agent for the formation of spherical hybrid nanostructures. This unique structure endows the V2O3/C hollow nanosphere hybrids with a dramatic increase in the BET surface area (132.9 m2 g−1; Figure S6), higher than the VOx rods (3.5 m2 g−1) and most VOx structures reported.8,20 This can be attributed to the overlap of the nanothorns on the surface shell of nanospheres. Most importantly, the nanothorns can increase the contact area between the electrode and electrolyte, theoretically expand and shrink freely, infiltrate due to the siphonic effect, and shorten the path length for ionic and electronic transport. The crystallographic structure of the various V2O3/C composites is examined by XRD. As displayed in Figure 2a, the diffraction peaks including (012), (104), (110), (006), (113), (024), (116), (214), and (300) can be well indexed as V2O3 (JCPDS no. 34-0187), which confirms that no impurities are formed.23,28 Raman spectra in Figure 2b show that the peaks below 1000 cm−1 in the V2O3/C hybrid are attributed to vanadium oxides. Two peaks at approximately 1310 and 1595 11240

DOI: 10.1021/acssuschemeng.7b01640 ACS Sustainable Chem. Eng. 2017, 5, 11238−11245

Research Article

ACS Sustainable Chemistry & Engineering Scheme 1. Schematic Illustration of the Facile Synthesis of the V2O3/C Hollow Nanospheres Hybrida

a I and II represent the solvothermal reaction, during which the vanadium−glucose spherical precursors were obtained; III to V are the carbothermal reduction progress, during which the inner part of the sphere gradually dissolved to form an urchin-like hollow nanosphere structure.

Figure 3. (a) Charge and discharge profile of the V2O3/C hybrid electrode for the first five cycles at a current density of 100 mA g−1. (b) Rate performance of the VOx nanorods and V2O3/C nanosphere electrode from 100 to 10000 mA g−1. (c) EIS measurements of the V2O3/C hybrid electrode and VOx rods electrode at open current voltage. (d) Cycling performance of the V2O3/C hybrid electrode at a current density of 1000 mA g−1 for 1000 cycles and the corresponding Coulombic efficiency. (e) Cyclic voltammogram curves of as-prepared V2O3/C hybrid electrode for the 1st, 2nd, and 3rd cycle at a scanning rate of 0.1 mV s−1. (f) Schematic illustration of the lithiation/delithiation process for the V2O3/C hybrid electrode.

a new peak at 982 cm−1 ascribed to the symmetric stretching vibration of V(III)O for the V2O3/C hybrid can be detected.33 It indicates that the precursor was transformed to V2O3 through a carbon thermal reduction process. Based on the

decomposition of the carbonaceous component during calcination. Moreover, the absorption peaks between 800 and 600 cm−1 in all the precursors correspond to the stretch vibrations of V(V)O. It could disappear after calcination, and 11241

DOI: 10.1021/acssuschemeng.7b01640 ACS Sustainable Chem. Eng. 2017, 5, 11238−11245

Research Article

ACS Sustainable Chemistry & Engineering

a current density as high as 5000 mA g−1, the capacity of the V2O3/C electrode can still maintain 483 mAh g−1; however, the specific capacity of the VOx electrode rapidly declines to about 230 mAh g−1. Remarkably, after testing the rate performance, 94.5% of the original capacity is recovered (1218 mAh g−1) when coming back to 100 mA g−1, while the recovery ratio of VOx is merely 66.3%. The excellent structural and cycle stability of V2O3/C hydrids indicates fast kinetics for the intercalation− deintercalation of LIB. For comparison, V2O3/C hybrids synthesized from different amounts of glucose (V2O3/C-1: 0.5 mmol and V2O3/C-2: 2 mmol) were also applied as the anode of the LIB shown in Figure S15; the V2O3/C-1 and V2O3/C-2 exhibit lower capacity than V2O3/C, which may due to the structural incompleteness. The EIS of the V2O3/C electrode as well as VOx rods are shown in Figure 3c. Apparently, the cycled battery has a higher charge-transfer resistance (Rct) than that of the cell at open current voltage (OCV). The CV profiles of the hollow nanospheres were acquired in the potential range 0.01 to 3.0 V at a scanning rate of 0.2 mV s−1. The electrochemical insertion/deinsertion mechanism of V2O3 can be described as follows:

above analysis, the overall reaction equation for the formation processes of the V2O3/C hybrid can be concluded as eqs 1 and 2: 2NH4 + + 3VO3− = V3O8− + 2NH3 + H 2O

(1)

4V3O8− + 2(C6H12O6 )n = (12n − 7)C + 7CO2 + 6V2O3 + 12nH 2O

(2)

It can be obviously observed that the initial bulk structures were gradually transferred to nanospheres with the lengthening of solvothermal reaction time as evidenced in the SEM images in Figure S12, because glucose can easily hydrolyze and polymerize to carbonaceous microspheres under the solvothermal reaction conditions.34−36 Moreover, the VOx nanorods but not hollow nanospheres could be obtained in the absence of glucose, further indicating the structural direction role of glucose in the formation of V2O3/C hollow sphere nanostructures. Additionally, to investigate the effect of the glucose usage amount on the formation of spherical nanostructures, the samples derived from different dosages of glucose by a solvothermal reaction were also synthesized for comparison (SEM images show in Figure S13). It can be observed that the sample composed both lamellar and spherical nanostructures when using a small amount of glucose, and homogeneous spherical structures formed gradually with the increase of glucose amount. When the amount of glucose is up to 10 mmol or more, the resultant sample exhibits larger and inhomogeneous nanospheres. It is demonstrated that the moderate usage amount of glucose plays a vital role for the formation of spherical structures. The precursor treated with different thermal treatment times was also studied. As it is shown in Figure S14 that the surface of the sphere is rough, and a few V2O3 nanoparticles can be observed obviously after calcination for 30 min. More importantly, a relatively smaller cavity volume in the nanospheres can be seen clearly. Then, the cavity volume is gradually enlarged, and the V2O3 nanoparticles on the surface of spheres are epitaxial grown to form nanofibers, resulting in the formation of an urchin-like V2O3/C hollow nanosphere hybrid. To sum up, the formation mechanism of V2O3/C hollow nanospheres is illustrated in Scheme 1. Initially, a vanadium− glucose spherical precursor is formed during the solvothermal reaction. Subsequently, the inner part of the sphere was gradually isolated and set apart to form a yolk−shell structure during the carbothermal reduction process. Ultimately, the inner part of the sphere gradually dissolved and diffused to the surface of the spherical structure; urchin-like hollow nanospheres were obtained. The charge and discharge profiles of V2O3/C for the initial five cycles (current density of 100 mA g−1) are exhibited in Figure 3a. The V2O3/C shows an initial discharge capacity of 1420 mAh g−1 and charge capacity of 1306 mAh g−1 with a Coulombic efficiency of 91.9%. The loss of capacity is mainly caused by the solid electrolyte interface (SEI) during the initial cycle.26 The rate performance of the V2O3/C electrode and VOx are explored at different current densities ranging up from 100 mA g−1 to as high as 10 000 mA g−1. As shown in Figure 3b, the V2O3/C electrode delivers higher capacity than that of VOx at every current density. The capacity of V2O3/C hollow nanospheres is 634 mAh g−1(1 A g−1), approximately 5 times higher than that of VOx nanorods (121 mAh g−1) and 1.7 times higher than that of graphite (372 mAh g−1). Moreover, even at

V2O3 + x Li+ + x e− = LixV2O3

(3)

LixV2O3 + (6 − x)Li+ + (6 − x)e− = 2V + 3Li 2O

(4)

Three peaks clearly appeared at voltage potentials of 0.6, 1.3, and 1.7 V in the initial cathodic cycle and disappeared in the following two cycles, which could be ascribed to the irreversible reaction related to electrolyte decomposition, the initial reduction of V2O3 to metallic vanadium, and the formation of an SEI layer. The broad peak at 1.25 V can be attributed to the oxidation of metallic vanadium. Then, for the subsequent two cycles, the CV curves can almost be overlapped, which indicates good reversibility of the V2O3/C electrode during the electrochemical process. The cycling performance of the V2O3/C electrode is displayed in Figure 3d. Notably, when cycling at 1000 mAh g−1 for 1000 cycles, the V2O3/C electrode shows an increase of capacity from 900 to 1250 mAh g−1, which could be ascribed to, during the long cycles, the unique hollow structure making better contact with the electrolyte, furthermore enhancing the transmission rate of the lithium ion, which can also be found in many metal oxide anode materials and hollow structures.37−42 In order to explore and characterize the structure and morphology variation of the electrode, the battery was dissembled inside the glovebox after the cycling finished. The SEM image of the V2O3/C electrode after 1000 cycles is shown in Figure S16. Although the nanospheres turned out to be a little more nonuniform, the spherical structure was seen to be retained after continuous charge and discharge cycles; morover, such good structural stability can guarantee the prolonged cycling stability. Schematic illustrations of the lithiation/delithiation process for V2O3/C were deduced and are shown in Figure 3f with the contrast with VOx nanorods shown in Figure S17. During the lithiation and delithiation progress, the VOx nanorods may suffer from the collapse of the structure and self-aggregation, which may induce poor cycle performance. While for the V2O3/C hollow spheres, the Li+ can embed into peripheral lamellar structures of the V2O3 hollow nanospheres, which are connected to the hollow spherical shell. The crossing and overlapped lamellar structure can buffer the volume variation during the consecutive lithiation/delithiation process. Meanwhile, the void formed from the overlapping lamellar structure is beneficial for the infiltrating of the 11242

DOI: 10.1021/acssuschemeng.7b01640 ACS Sustainable Chem. Eng. 2017, 5, 11238−11245

Research Article

ACS Sustainable Chemistry & Engineering

Figure 4. (a) Schematic illustration of the full battery based on the V2O3/C anode and commercial LiMn1/3Co1/3Ni1/3O2 cathode. (b) Voltage profile of the full battery cycled between 2.0 and 4.7 V at a rate of 100 mA g−1. (c) Rate performance of the as-assembled full cell. (d) Photograph of a single LED being powered by a coin cell battery.

stress coming from volume variation during the electrochemical processes. Second, the amorphous carbon on the surface of the nanostructure contributes to better electrical conductivity and is beneficial to maintaining structure integrity, which is advantageous for the transport of lithium ions and electrons. Third, the thorns on the surface of the nanosphere enlarge the active surface area, provide more lithium ion storage sites, and make better contact with the electrolyte, furthermore guaranteeing the transmission rate of lithium ions.

electrolyte and the fast transfer of lithium ions and electrons. Additionally, part of the Li+ can embed directly into the shell (containing V2O3 and amorphous carbon). Then, two kinds of Li+ can form reflux along the hollow spherical shell, which will not collapse the structure of the hollow sphere due to the stable amorphous carbon in the shell. To demonstrate this electrode material’s suitability for practical applications,43,44a full cell was assembled using V2O3/C as the anode electrode and commercial high-voltage LiMn1/3Co1/3Ni1/3O2 as the cathode. The cell performance was examined at a charge/discharge current density of 100 mA g−1 at a voltage range of 2.0−4.7 V as shown in Figure 4b. The cell exhibits an excellent performance of 197.2 mAh g−1, and a high capacity of 106 mAh g−1 remained after 50 cycles, as shown in Figure 4c. A 3 V, 10 mW blue light emitting diode (LED) can be lit and maintained for 12 h (Figure 4d). Given the initial capacity of 198 mAh g−1, the energy density of the V2O3/C electrode is as high as 740 Wh kg−1 with a power rate of 375 W kg−1, which is higher that of common intercalation compounds such as LiFePO4 (580 Wh kg−1) and LiMn2O4 (590 Wh kg−1). All the results demonstrate that our urchin-like V2O3/C hollow nanospheres can be promising high-performance lithium anodes. The electrochemical properties of our V2O3/C nanostructure and various reported V2O3-based materials in lithium ion batteries are compared and shown in Table S1. Our synthesis method has obvious advantages, as most reported methods are relatively harsh, involving environmentally unfriendly organic solvents. Moreover, most reaction temperatures are higher than 200 °C, which is unsuitable for mass production. In addition, most reported V2O3 material is large in size, and there is not much control in the structure. The above results show that the outstanding performance of the urchin-like V2O3/C hollow nanospheres can be attributed to its structural virtue. First, the unique structure of the hollow nanosphere with nanothorns on the surface can hinder harmful self-aggregation and relieve the

■

CONCLUSIONS

In summary, a V2O3/C hybrid composed of nanofibers and hollow nanospheres has been successfully synthesized. Glucose could play the role of a carbon resource, a reducing agent for carbothermal reaction, and a structural direction role for the formation of hollow spheres. The amorphous carbon shell is beneficial for the structural stability and conductivity of the entire nanostructure, contributing to low charge transfer resistance and high electronic transport. Meanwhile, the hollow sphere nanostructure of the V2O3/C hybrid is responsible for accommodation of the volume variation during the insertion and extraction of Li ions. As for LIB anodes, the V2O3/C hybrid shows high reversible capacity, outstanding cycling stability, and extraordinary rate capability owing to the advantages of the special nanostructures. Moreover, the full cell assembled using V2O3/C as the anode and a commercial LiMn1/3Co1/3Ni1/3O2 cathode exhibits excellent cycling performance and high capacity, indicating its great potential application as an electrode for LIBs. Our simple and robust synthetic strategy can be extended for the preparation of other metal oxide hollow sphere structures as the electrode materials for high-performance LIBs. 11243

DOI: 10.1021/acssuschemeng.7b01640 ACS Sustainable Chem. Eng. 2017, 5, 11238−11245

Research Article

ACS Sustainable Chemistry & Engineering

■

(10) Li, W.; Liu, J.; Zhao, D. Y. Mesoporous Materials for Energy Conversion and Storage Devices. Nat. Rev. Mater. 2016, 1, 16023. (11) Chen, G.; Yan, L. T.; Luo, H. M.; Guo, S. J. Nanoscale engineering of heterostructured anode materials for boosting lithiumion storage. Adv. Mater. 2016, 28 (35), 7580−7602. (12) Niu, C. J.; Meng, J. S.; Han, C. H.; Zhao, K. N.; Yan, M. Y.; Mai, L. Q. VO2 Nanowires assembled into hollow microspheres for highrate and long-life lithium batteries. Nano Lett. 2014, 14 (5), 2873− 2878. (13) Zhai, T.; Lu, X.; Ling, Y.; Yu, M.; Wang, G.; Liu, T.; Liang, C.; Tong, Y.; Li, Y. A new benchmark capacitance for supercapacitor anodes by mixed-valence sulfur-doped V6O13−x. Adv. Mater. 2014, 26 (33), 5869−5875. (14) He, H. Y.; Fu, W.; Wang, H. T.; Wang, H.; Jin, C. H.; Fan, H. J.; Liu, Z. Silica-modified SnO2-graphene ‘slime’ for self-enhanced Li-ion battery anode. Nano Energy 2017, 34, 449−455. (15) Wei, Q. L.; Tan, S. S.; Liu, X. Y.; Yan, M. Y.; Wang, F. C.; Li, Q. D.; An, Q. Y.; Sun, R. M.; Zhao, K. N.; Wu, H. G.; Mai, L. Q. Novel polygonal vanadium oxide nanoscrolls as stable cathode for lithium storage. Adv. Funct. Mater. 2015, 25 (12), 1773−1779. (16) Sun, Y.; Qu, B.; Jiang, S.; Wu, C.; Pan, B.; Xie, Y. Highly depressed temperature-induced metal-insulator transition in synthetic monodisperse 10-nm V2O3 pseudocubes enclosed by {012} facets. Nanoscale 2011, 3 (6), 2609−2614. (17) Pan, A. Q.; Wu, H. B.; Yu, L.; Lou, X. W. Template-free Formation of Uniform VO2 Hollow Microspheres with Different Interiors and Their Conversion to V2O5 for Lithium-ion Batteries. Angew. Chem., Int. Ed. 2013, 52 (8), 2226−2230. (18) Zhou, X.; Wan, L. J.; Guo, Y. G. Binding SnO2 nanocrystals in nitrogen-doped graphene sheets as anode materials for Lithium-ion batteries. Adv. Mater. 2013, 25 (15), 2152−2157. (19) Xu, S. M.; Hessel, C. M.; Ren, H.; Yu, R. B.; Jin, Q.; Yang, M.; Zhao, H. J.; Wang, D. α-Fe2O3 multi-shelled hollow microspheres for lithium ion battery anodes with superior capacity and charge retention. Energy Environ. Sci. 2014, 7 (2), 632−640. (20) Gu, D.; Li, W.; Wang, F.; Bongard, H.; Spliethoff, B.; Schmidt, W.; Weidenthaler, C.; Xia, Y. Y.; Zhao, D. Y.; Schuth, F. Controllable synthesis of mesoporous peapod-like Co3O4@Carbon nanotube arrays for high-performance Lithium-ion batteries. Angew. Chem. 2015, 127 (24), 7166−7170. (21) Liu, J.; Jiang, J.; Cheng, C.; Li, H. X.; Zhang, J. X.; Gong, H.; Fan, H. J. Co3O4 Nanowire@MnO2 ultrathin nanosheet core/shell arrays: A new class of high-performance pseudocapacitive materials. Adv. Mater. 2011, 23 (18), 2076−2081. (22) Wang, Z.; Zhou, L.; Lou, X. W. Metal oxide hollow nanostructures for Lithium-ion batteries. Adv. Mater. 2012, 24 (14), 1903−1911. (23) Niu, C. J.; Huang, M.; Wang, P. Y.; Meng, J.; Liu, X.; Wang, X. P.; Zhao, K. N.; Yu, Y.; Wu, Y. Z.; Lin, C.; Mai, L. Q. Carbonsupported and nanosheets-assembled vanadium oxide microspheres for stable lithium ion battery anodes. Nano Res. 2016, 9 (1), 128−138. (24) Jiang, L.; Qu, Y.; Ren, Z. Y.; Yu, P.; Zhao, D. D.; Zhou, W.; Wang, L.; Fu, H. G. In situ carbon-coated yolk−shell V 2O 3 microspheres for Lithium-ion batteries. ACS Appl. Mater. Interfaces 2015, 7 (3), 1595−1601. (25) Park, M. S.; Wang, G. X.; Kang, Y. M.; Wexler, D.; Dou, S. X.; Liu, H. K. Preparation and electrochemical properties of SnO2 nanowires for application in Lithium-ion batteries. Angew. Chem. 2007, 119 (5), 764−767. (26) Wang, C.; Zhou, Y.; Ge, M.; Xu, X.; Zhang, Z.; Jiang, J. Largescale synthesis of SnO2 nanosheets with high lithium storage capacity. J. Am. Chem. Soc. 2010, 132 (1), 46−47. (27) Wang, L.; He, X.; Li, J.; Sun, W.; Gao, J.; Guo, J.; Jiang, C. Nano-structured phosphorus composite as high-capacity anode materials for lithium batteries. Angew. Chem. 2012, 124 (36), 9168− 9171. (28) Li, X. X.; Fu, J. J.; Pan, Z. G.; Su, J. J.; Xu, J. W.; Gao, B.; Peng, X.; Wang, L.; Zhang, X. M.; Chu, P. K. Peapod-like V2O3 nanorods

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b01640. SEM images, FT-IR curve, Raman, TG, and N 2 adsorption−desorption isotherms (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected], [email protected]. ORCID

Haitao Yu: 0000-0003-3764-9201 Honggang Fu: 0000-0002-5800-451X Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work is supported by the National Natural Science Foundation of China (21631004, 21771059, 21371053, 21401048, 51672073), the Natural Science Foundation of Heilongjiang Province (B2017008), the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province (UNPYSCT-2016016), the Project for Foshan Innovation Group (2014IT100062), and the Harbin Science and Technology Innovation Talents Research Foundation (2015RAQXJ057).

■

REFERENCES

(1) Mai, L.; Tian, X.; Xu, X.; Chang, L.; Xu, L. Nanowire electrodes for electrochemical energy storage devices. Chem. Rev. 2014, 114 (23), 11828−11862. (2) Liu, P. C.; Zhu, K. J.; Gao, Y. F.; Luo, H. J.; Lu, L. Recent progress in the applications of vanadium-based oxides on energy storage: from low-dimensional nanomaterials synthesis to 3D micro/ nano-structures and free-standing electrodes fabrication. Adv. Energy Mater. 2017, 1700547. (3) Mahmood, N.; Tang, T.; Hou, Y. Nanostructured anode materials for lithium ion batteries: progress, challenge and perspective. Adv. Energy Mater. 2016, 6, 1600374. (4) Liu, X.; Chao, D.; Su, D.; Liu, S.; Chen, L.; Chi, C.; Lin, J.; Shen, Z. X.; Zhao, J.; Mai, L.; Li, Y. Graphene nanowires anchored to 3D graphene foam via self-assembly for high performance Li and Na ion storage. Nano Energy 2017, 37, 108−117. (5) Wang, F.; Wu, X.; Li, C.; Zhu, Y.; Fu, L.; Wu, Y.; Liu, X. Nanostructured positive electrode materials for post-lithium ion batteries. Energy Environ. Sci. 2016, 9, 3570−3611. (6) Zuo, X. X.; Zhu, J.; Müller-Buschbaum, P.; Cheng, Y.-J. Silicon based lithium-ion battery anodes: A chronicle perspective review. Nano Energy 2017, 31, 113−143. (7) Liu, N.; Lu, Z.; Zhao, J.; McDowell, M. T.; Lee, H.-W.; Zhao, W.; Cui, Y. A pomegranate-inspired nanoscale design for large-volumechange lithium battery anodes. Nat. Nanotechnol. 2014, 9 (3), 187− 192. (8) Wang, B.; Li, X.; Qiu, T.; Luo, B.; Ning, J.; Li, J.; Zhang, X.; Liang, M.; Zhi, L. High volumetric capacity silicon-based lithium battery anodes by nanoscale system engineering. Nano Lett. 2013, 13 (11), 5578−5584. (9) Koo, B.; Kim, H.; Cho, Y.; Lee, K.; Choi, N.; Cho, J. A highly cross-linked polymeric binder for high-performance silicon negative electrodes in lithium ion batteries. Angew. Chem., Int. Ed. 2012, 51 (35), 8762−8767. 11244

DOI: 10.1021/acssuschemeng.7b01640 ACS Sustainable Chem. Eng. 2017, 5, 11238−11245

Research Article

ACS Sustainable Chemistry & Engineering encapsulated into carbon as binder-free and flexible electrodes in lithium-ion batteries. J. Power Sources 2016, 331, 58−66. (29) Gu, D.; Li, W.; Wang, F.; Bongard, H.; Schmidt, S. W.; Weidenthaler, C.; Xia, Y. Y.; Zhao, D. Y.; Schüth, F.; Spliethoff, B. Controllable synthesis of mesoporous peapod-like Co3O4@carbon nanotube arrays for high-performance lithium-ion batteries. Angew. Chem. 2015, 127 (24), 7166−7170. (30) Horrocks, G. A.; Braham, E. J.; Liang, Y.; De Jesus, L. R.; Jude, J.; Velázquez, J. M.; Prendergast, D.; Banerjee, S. Vanadium K-edge Xray absorption spectroscopy as a probe of the heterogeneous lithiation of V2O5: First-principles modeling and principal component analysis. J. Phys. Chem. C 2016, 120 (42), 23922−23932. (31) Liu, L.; Yao, T.; Tan, X.; Liu, Q.; Wang, Z.; Shen, D.; Sun, Z.; Wei, S.; Xie, Y. Room-temperature intercalation-deintercalation strategy towards VO2(B) single layers with atomic thickness. Small 2012, 8 (24), 3752−3756. (32) Lai, X.; Halpert, J. E.; Wang, D. Recent advances in micro-/ nano-structured hollow spheres for energy applications: From simple to complex systems. Energy Environ. Sci. 2012, 5 (2), 5604−5618. (33) Li, H.-Y.; Jiao, K.; Wang, L.; Wei, C.; Li, X.; Xie, B. Micelle anchored in situ synthesis of V2O3 nanoflakes@C composites for supercapacitors. J. Mater. Chem. A 2014, 2 (44), 18806−18815. (34) Xu, Y.; Zheng, L.; Wu, C.; Qi, F.; Xie, Y. New-Phased Metastable V2O3 Porous Urchinlike Micronanostructures: Facile Synthesis and Application in Aqueous Lithium Ion Batteries. Chem. Eur. J. 2011, 17 (1), 384−391. (35) Sun, X.; Li, Y. D. Colloidal carbon spheres and their core/shell structures with noble-metal nanoparticles. Angew. Chem. 2004, 116 (5), 607−611. (36) Sun, X.; Liu, J.; Li, Y. Use of carbonaceous polysaccharide microspheres as templates for fabricating metal oxide hollow spheres. Chem. - Eur. J. 2006, 12 (7), 2039−2047. (37) Lai, X.; Li, J.; Korgel, B. A.; et al. General synthesis and gassensing properties of multiple-shell metal oxide hollow microspheres. Angew. Chem. 2011, 123 (12), 2790−2793. (38) Zhou, X.; Yin, Y. X.; Wan, L. J.; Guo, Y. G. A robust composite of SnO2 hollow nanospheres enwrapped by graphene as a highcapacity anode material for lithium-ion batteries. J. Mater. Chem. 2012, 22 (34), 17456−17459. (39) Zhang, C.; Peng, X.; Guo, Z.; Cai, C.; Chen, Z.; Wexler, D.; Li, S.; Liu, H. Carbon-coated SnO2/graphene nanosheets as highly reversible anode materials for lithium ion batteries. Carbon 2012, 50 (5), 1897−1903. (40) Pan, A. Q.; Wu, H. B.; Zhang, L.; Lou, X. W. Uniform V2O5 nanosheet-assembled hollow microflowers with excellent lithium storage properties. Energy Environ. Sci. 2013, 6 (5), 1476−1479. (41) Wu, H. B.; Pan, A.; Hng, H. H.; Lou, X. W. Template-assisted Formation of Rattle-type V2O5 Hollow Microspheres with Enhanced Lithium Storage Properties. Adv. Funct. Mater. 2013, 23 (45), 5669− 5674. (42) Zhu, Q.; Wu, P.; Zhang, J.; Zhang, W.; Zhou, Y.; Tang, Y.; Lu, T. Cyanogel-derived formation of 3D nanoporous SnO2−MxOy(M = Ni, Fe, Co) hybrid networks for high-performance lithium storage. ChemSusChem 2015, 8 (1), 131−137. (43) Balogun, M.-S.; Qiu, W.; Luo, Y.; Meng, H.; Mai, W.; Onasanya, A.; Olaniyi, T. K.; Tong, Y. A review of the development of full cell lithium-ion batteries: The impact of nanostructured anode materials. Nano Res. 2016, 9 (10), 2823−2851. (44) Liu, B.; Zhang, J.; Wang, X.; Chen, G.; Chen, D.; Zhou, C.; Shen, G. Hierarchical three-dimensional ZnCo2O4 nanowire arrays/ carbon cloth anodes for a novel class of high-performance flexible lithium-ion batteries. Nano Lett. 2012, 12 (6), 3005−3011.

11245

DOI: 10.1021/acssuschemeng.7b01640 ACS Sustainable Chem. Eng. 2017, 5, 11238−11245