Synthesis and Electrochemical Performance of SnOx Quantum Dots

Research Article www.acsami.org

Synthesis and Electrochemical Performance of SnOx Quantum Dots@ UiO-66 Hybrid for Lithium Ion Battery Applications Weiyang Li,† Zhen Li,† Fan Yang, Xujun Fang, and Bohejin Tang* College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China S Supporting Information *

ABSTRACT: A novel method that combines the dehydration of inorganic clusters in metal−organic frameworks (MOFs) with nonaqueous sol−gel chemistry and pyrolysis processes is developed to synthesize SnOx quantum dots@Zr-MOFs (UIO-66) composites. The size of as-prepared SnO x nanoparticles is approximately 4 nm. Moreover, SnOx nanoparticles are uniformly anchored on the surface of the Zr-MOFs, which serves as a matrix to alleviate the agglomeration of SnOx grains. This structure provides an accessible surrounding space to accommodate the volume change of SnOx during the charge/discharge process. Cyclic voltammetry and galvanostatic charge/ discharge were employed to examine the electrochemical properties of the ultrafine SnOx@Zr-MOF (UIO-66) material. Benefiting from the advantages of the smaller size of SnOx nanoparticles and the synergistic effect between SnOx nanoparticles and the Zr-MOFs, the SnOx@Zr-MOF composite exhibits enhanced electrochemical performance when compared to that of its SnOx bulk counterpart. Specifically, the discharge-specific capacity of the SnOx@Zr-MOF electrode can still remain at 994 mA h g−1 at 50 mA g−1 after 100 cycles. The columbic efficiencies can reach 99%. KEYWORDS: SnOx, Zr-MOFs (UIO-66), nonaqueous sol−gel, high cycling stability, lithium ion batteries

1. INTRODUCTION Lithium-ion batteries (LIBs) have been used in electronic devices, hybrid electric vehicles, and future emerging smart grids because of their high power density and good cyclability.1−3 Tin oxide and metallic tin are generally considered as potential anode materials for LIBs to replace the commercially used graphite because of their several appealing properties, including availability of abundant resources, environmental benignity, low potential of Li+ intercalation, and high theoretical capacity (780 and 876 mA h g−1 for SnO2 and SnO).4−8 However, SnOx-based anodes suffer from rigorous capacity loss and inferior cycling performance because of the volume change (∼300%)4,5 during the lithiation/delithiation process. In addition, SnOx-based anodes usually suffer from large initial irreversible capacity induced by the solid electrolyte interphase (SEI) layer and the electrochemically inactive Li2O.9 Taking into account all of the above considerations, the reasonable design of the electrode materials’ microstructure is important for the electrochemical performance of SnOx-based electrode materials. To surmount the above deficiencies, two effective approaches have been applied. One is to decrease the size of SnOx materials down to the nanoscale, because nanosized particles can provide more insertion sites for Li ions, shorten the diffusion distances of Li ions, and better accommodate the absolute volume change. Another approach is to cover SnOx with an electrochemically stable protecting shell or to form SnOx carbon nanocomposites. This strategy can provide a physical barrier for the volume © 2017 American Chemical Society

change and the pulverization of particles. There are several examples of these two approaches in the literature, such as SnO2 and carbon composites using carbon hollow spheres and carbon tubes,10,11 graphene oxide wrapping the SnO2 hollow sphere,12 and nitrogen-doped porous carbon covering the ultrasmall Sn nanoparticles (∼5 nm).13 Various synthetic methods, such as the electrostatic spinning, thermal evaporation, high-energy ball milling, and magnetron sputtering,14−17 have been applied to construct SnOx-C architectures. However, the above synthetic strategies are complicated, time-consuming, and energy-intensive. In addition, the capacity decay may be remitted by utilizing these improved methods, but the high carbon matrix content and comparatively low SnOx content (usually less than 25%)18 lead to serious reduction of the specific capacity. Undoubtedly, for higher specific capacity, better rate capability, and better cycling performance, it is desirable to have high nanosized SnOx as well as a high dispersion of the SnOx nanoparticles in the composite. Metal−organic frameworks (MOFs) are a series of microporous materials that have been applied in various fields including gas separation and storage, sensing, catalysis, energy storage, and so on.19−22 MOFs consist of metal ion nodes linked together by multitopic organic ligands, which provide the advantage of tunable porosities and versatile functionalities. Received: August 4, 2017 Accepted: September 14, 2017 Published: September 14, 2017 35030

DOI: 10.1021/acsami.7b11620 ACS Appl. Mater. Interfaces 2017, 9, 35030−35039

Research Article

ACS Applied Materials & Interfaces Scheme 1. Schematic Diagram of the Synthetic Route of SnOx@Zr-MOFsa

a

Red: O; blue: Zr; light blue: H. The other parts of the sol molecule are represented by a green rectangle.

In addition, MOFs are promising materials to support metals and metal oxides because of their large specific areas, high pore volumes, and inorganic−organic hybrid nature.23 In recent years, the use of MOFs as a sacrificial precursor to prepare highly dispersed nanoporous carbon materials or to serve as a protecting shell on metal oxide nanoparticles has been described.22 For example, Cheng and co-workers prepared NiP2@C grains by carbonizing a Ni-based metal−organic framework that had adsorbed red phosphorus. The as-obtained nanostructured NiP2@C showed a discharge-specific capacity of 656 mA h g−1 at 50 mA g−1 up to 50 cycles.24 Han’s group synthesized SnO2 nanoparticles by calcining the tin MOF precursors, and the capacity was about 541.8 mA h g-1 under 400 mA g under 400 mA g−1 after 100 cycles.25 Wang and coworkers prepared SnO2@C nanocomposites by introducing Sn2+ into the channels of HKUST-1 and then by calcination to form SnO2.26 The discharge capacity of the product can reach 880 mA h g−1 at 100 mA g−1, which is more than twice that of commercial graphite anodes (372 mA h g−1). However, these methods suffer from a common problem that the structure of MOFs can be destroyed after forming the composites and thus the advantage of using the MOF matrix is lost. In this paper, a novel and facile method to prepare a homogeneous dispersion SnOx nanoparticles on the surface of UIO-66 (Zr6O4(OH)4(bdc)6; bdc2− = 1,4-benzenedicarboxylate) was developed. This approach takes advantage of postsynthetic modification, the high thermal stability (up to 773 K),27 the porous structure, and the outstanding electrochemical stability of Zr-MOFs. The method involves three procedures, including vacuum drying the Zr-MOFs (573 K), sol−gel processing, and pyrolysis processing. We report here the first example of a SnOx@Zr-MOF composite anode material with both excellent rate capability and good cyclability. The specific capacity of the composite can still remain at 994 mA h g−1 at 50 mA g−1 after 100 cycles. In addition, the processing strategy is convenient, inexpensive, and time-saving. Combining with advantages of the synthetic method and the electrochemical performance, the SnOx@Zr-MOF composites exhibit promising applications as anodes for LIBs.

times, respectively. The final products were dried under vacuum (120 °C, 24 h). 2.2. Synthesis of SnOx@Zr-MOF Composites and Dehydration of Zr-MOFs. The white Zr-MOF powder (0.05 g) was put into a glass flask and dried at 300 °C under vacuum for 6 h to eliminate water molecules from the cluster core and generate coordinatively unsaturated Zr4+ sites. Then, 1.5 g of SnCl2·2H2O was dissolved in 10 mL of tetrahydrofuran (THF) with the help of ultrasonication to prepare the Sn-based precursor solution. The above solution was poured into the above flask that contained the dehydrated Zr-MOF powders as soon as possible and kept in the air (300 °C, 0.5 h) to convert the stannate to tin oxides. Finally, the gray-black samples were obtained by washing (ethanol, 10 times) and drying (80 °C for 20 h, in vacuum). 2.3. Synthesis of SnOx Nanoparticles. Nanophase SnOx was prepared by the same method as the SnOx@Zr-MOF products. The only difference was that Zr-MOF powder was not added in the above glass flask. 2.4. Characterization and Electrochemical Testing. The composition of all products was investigated by X-ray diffraction (XRD, Bruker D2 Phaser X-Ray Diffractometer, Cu Kα radiation). The micromorphologies and nanostructures of Zr-MOF, SnOx, and SnOx@ Zr-MOF composites were further investigated using a Hitachi S4800 scanning electron microscope and a Hitachi H-800 transmission electron microscope. Elemental mapping was carried out by X-ray spectroscopy on the Hitachi H-800. The N2 adsorption−desorption isotherms were performed using liquid N2 by the Micromeritics ASAP 2460 analyzer with a degassing temperature of 473 K.The specific surface areas and porosity property were analyzed by Brunauer− Emmett−Teller (BET) equation and the Barrett-Joyner-Halenda model, respectively. The samples were also examined by X-ray photoelectron spectroscopy (XPS, Thermo ESCALAB 250XI equipped with an Al Kα X-ray source) To prepare the electrode, active materials, conductive materials (acetylene black), and binders (poly(vinylidene difluoride)) at a weight percent ratio of 8:1:1 were mixed and then pasted onto a Cu foil (1.1 cm2). A lithium foil was used as the counter electrode. The electrolyte was 1 M LiPF6 dissolved in dimethyl carbonate and ethylene carbonate (1:1, v/v). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) curves were tested by the CHI660D electrochemical workstation at room temperature. The charge/discharge measurements were carried out on the NEWARE CT-3008 instrument, and the voltage range was 0.01−3.0 V.

2. EXPERIMENTAL SECTION

3. RESULTS AND DISCUSSION In this study, SnOx nanoparticles were synthesized through a nonaqueous sol−gel method. Compared with the complex aqueous sol−gel process, the nonaqueous process can keep the nanomaterials with homogeneous particle morphologies. Generally, in a nonaqueous system, the oxygen for nanometal oxide formation is provided by the solvent, such as ethers, alcohols, ketones, and aldehydes.28 Therefore, THF was employed as the solvent. The reactions between SnCl2·2H2O

2.1. Synthesis of the Zr-MOF Nanoparticles. Zr-MOF nanoparticles were prepared according to our group’s previous report with a slight modification.27 ZrCl4 (0.227 mmol) was dissolved in 30 mL of N,N-dimethylformamide (DMF, 99%) in a 100 mL roundbottom flask to form a clear solution, and then 0.227 mmol terephthalic acid was added to this solution. The mixture was heated to 70 °C and stirred at 600 rpm for 2 weeks. The resulting white powder was isolated by centrifugation (12 000 rpm, 10 min) and washed with 10 mL of DMF and 10 mL of anhydrous methanol three 35031


Research Article

ACS Applied Materials & Interfaces

Figure 1. (a) XRD patterns of Zr-MOFs, SnOx, and SnOx@Zr-MOFs. (b) Full scan XPS spectra of SnOx and SnOx@Zr-MOFs. Inset: highresolution XPS spectra of Sn 3d5/2 for SnOx@Zr-MOFs.

The scanning electron microscopy (SEM) images in Figure 2a,b display the morphologies of as-synthesized Zr-MOFs and SnOx@Zr-MOFs. The image in Figure 2a shows that the ZrMOF crystals exhibited an octahedral structure with an average diameter of about 50 nm. Moreover, the crystals were almost evenly distributed. The rough surface of SnOx@Zr-MOFs indicates that SnOx nanoparticles are present on the surface of MOFs. Such morphologies and structures have been maintained after SnOx nanoparticle loading, as manifested by SEM and transmission electron microscopy (TEM) images in Figure 2b,c. The SnOx nanoparticles can be observed from TEM as well and were uniformly distributed in the Zr-MOF crystals without obvious aggregation (Figure 2d). In contrast, the bulk SnOx counterpart was clustered together because of the lack of the Zr-MOF matrix (Figure 2e). Moreover, the lattice fringes of SnOx were clearly observed in the highresolution TEM (HRTEM) image, and the size of the SnOx nanoparticles was less than 5 nm, which was much smaller than that of previously reported materials (Figure 2d,e),38,39 indicating that the nonaqueous sol−gel method can prepare ultrafine nanomaterials and keep the nanomaterials with homogeneous particle morphologies. All of the elements of the SnOx@Zr-MOF composite can be detected by the energydispersive X-ray (EDX) analysis (Figure 2f), indicating the coexistence of Zr-MOFs and SnOx. To show the spatial distribution of SnOx in the SnOx@Zr-MOF composite, elemental mapping was performed (Figure 2g). As shown in Figure 2h−k, all elemental mapping images exhibit a uniform distribution of the carbon, oxygen, zirconium, and tin elements in the composite, further testifying that SnOx nanoparticles homogeneously dispersed on the Zr-MOF matrix. N2 adsorption−desorption isotherms and the pore-size distributions of SnOx@Zr-MOFs, SnOx, and Zr-MOFs were performed and are shown in Figure 3. It can be observed that a rapid nitrogen uptake starts with 0.06 with a low relative pressure. The isotherm exhibits type I characteristics, suggesting typical microporous behavior (Figure 3a).40 The BET surface areas and the maximum pore volume of Zr-MOFs are 1014 m2 g−1 and 0.5 cm3 g−1, respectively. It is noteworthy that the BET surface areas of SnOx@Zr-MOFs are 50 m2 g−1,

and THF precursors to form the metal−oxygen−metal bond could be described as follows

When Zr-MOF was heated under dynamic vacuum, both physically adsorption water and solvent molecules were eliminated from the pores to generate Zr6O6 units, while keeping the integrity of the crystal lattice structure.29,30 The coordinatively unsaturated Zr4+ sites then behave as strong Lewis acid sites.29,31,32 The sol molecules served as the linkers. With the growth of sol molecular chains and the sudden increase in temperature, the gel molecules decomposed to SnO nanoparticles. Because the reaction was carried out in air, a part of SnO could be converted to SnO2 to form the SnOx composite. The schematic diagram of the SnOx@Zr-MOF composite formation is shown in Scheme 1. The composition and structure of the products was analyzed by XRD. In Figure 1a, the main diffractions of the as-synthesized Zr-MOFs matched with the simulated ones and no impurity peaks could be detected. Notably, the diffraction peak at 2θ = 7° marked with a red triangle corresponding to SnOx@Zr-MOFs was still present, suggesting that the framework of Zr-MOFs was maintained well during the whole synthetic process. Moreover, although no diffractions were detected for SnO or SnO2 in SnOx and SnOx@Zr-MOFs composites, three strong diffraction peaks marked with plum blossom were assigned to the SnO2 and SnO (JCPDS card Nos. 46-1088 and 07-0195). It was probably caused by the formation of the small SnOx nanoparticles. A similar phenomenon was also found in previously reported nanoparticle@MOFs composites.33−35 To further prove the presence of SnO and SnO2, XPS was applied to identify the chemical states of the composite. As shown in Figure 1b, the peaks of O, C, Sn, and Zr elements were observed in the XPS spectra of SnOx@Zr-MOFs. Moreover, the Sn 3d5/2 was divided into two fitted peaks at 487.5 and 486.8 eV corresponding to the Sn4+ and Sn2+, respectively.36,37 The XPS results were consistent with the XRD measurements. Both XRD and XPS characterizations confirmed that SnOx hybrids had been successfully prepared. 35032


Research Article


Figure 2. continued

35033


Research Article


Figure 2. SEM images of the Zr-MOFs (a) and SnOx@Zr-MOFs (b). TEM images of the SnOx@Zr-MOFs (c). High-resolution TEM images of SnOx@Zr-MOFs (d) and SnOx (e). TEM images of SnOx@Zr-MOFs (f) with the corresponding EDX analysis (g) and (h−k) elemental mapping of C, O, Zr, Sn, respectively.

which are higher than that of SnOx (3 m2 g−1) but much lower than that of the Zr-MOFs (1014 m2 g−1) (Figure 3c). This indicates that the SnOx nanoparticles have been successfully loaded on the Zr-MOFs, blocking most of the pores of the ZrMOFs, so that the specific surface area decreases. The SnOx@ Zr-MOFs and SnOx samples have a pore-size distribution centered at 2 and 1.8 nm, respectively. The mesoporous structure can allow the lithium ion and electrolyte species to diffuse through the structure during the cycling (Figure 3). The results show the formation of a porous structure in the SnOx sample, which may be attributed to textural mesoporosity between individual particles in the aggregates. Such a high surface area and porous host architectures are favorable for electrochemical performance because the high specific area can not only promote more Li ions into the electrode material through the active sites, but also assure locally lower current

densities and make higher charge−discharge rates without capacity loss.41 The electrochemical performance of the SnOx@Zr-MOFs electrode was analyzed through CV, as depicted in Figure 4. As a typical metal oxide anode material, it has been widely accepted that SnO and SnO2 experience similar reactions in lithiation/delithiation processes,42−45 as follows SnO + 2Li+ + 2e− → Sn + Li 2O

(1)

SnO2 + 4Li+ + 4e− → Sn + 2Li 2O

(2)

Sn + x Li+ + x e− ↔ LixSn (0 < x < 4.4)

(3)

In the first cycle, the cathodic peak at around 0.65 V is attributed to the formation of the SEI layer on the surface of the SnOx@Zr-MOF electrode.46 In addition, the reduction peaks at about 1.05 V corresponds to the reduction of SnOx to 35034


Research Article


Figure 3. Nitrogen adsorption and desorption isotherms of SnOx@Zr-MOFs (a), SnOx (b), and Zr-MOFs (c). Insets: corresponding pore-size distribution curves.

Sn, and the reduction peaks at about 0.12 V can be ascribed to the formation of Li−Sn alloys, as described in eqs 1−3.4,47 Generally, the reduction process of the formation of SEI and SnOx to Sn is considered to be irreversible, resulting in a large irreversible capacity in the first cycle.48 During the first charging process, an obvious oxidation peak around 0.51 V corresponds to the dealloying from the Li−Sn alloy. Another broad oxidation peak at 1.25 V can be attributed to the partially reversible reaction of Sn to SnOx.47,48 As can be seen, the CV curves almost overlapped during the following cycles, demonstrating the superior cyclability of the SnOx@Zr-MOF electrode. Figure 5a,b shows charge/discharge sweeps of SnOx@ZrMOF and SnOx electrodes, respectively. In the first discharge curve, SnOx@Zr-MOF and SnOx electrodes exhibit two similar potential plateaus at about 1.2 and 0.8 V, which are associated with the reduction of SnOx to Sn and the formation of amorphous Li2O. The long flat curves for the above two electrodes from 0.5 to 0.01 V correspond to the reaction of Sn and Li. The discharge capacities of the SnOx@Zr-MOF electrode are 2590, 1424, 1351, 1299, and 1269 mA h g−1 from 1st to 5th, respectively. However, for the SnOx electrode,

Figure 4. CV curves of SnOx@Zr-MOFs.

35035


Research Article


Figure 5. Discharge−charge profiles of the SnOx@Zr-MOF (a) and SnOx (b) electrodes at a current density of 50 mA g−1. (c) Rate performance tests of the SnOx@Zr-MOF and SnOx electrodes. (d) Cycling performance of SnOx@Zr-MOFs and SnOx at 50 mA g−1. (e) Discharge−charge profiles of dehydration Zr-MOFs at 50 mA g−1. (f) Rate performance test of the dehydration Zr-MOFs. (g) Electrochemical impedance spectra of the SnOx@Zr-MOF and SnOx electrodes. (h) Magnified view of the Nyquist curves. 35036


Research Article


importantly, the average capacity during the 100 cycles is 1033 mA h g−1. The corresponding Coulombic efficiency of the SnOx@Zr-MOF electrode is also displayed in Figure 5d, and the average can be up to 97%. Simultaneously, the cycling retention and capacity are clearly better than some of the previous reports, and their synthesis methods are much more complicated and energy-intensive.51−53 Interestingly, an increasing trend in capacity is observed during the later cycles from the 65th to the 90th cycle, as shown in Figure 5d. The enhanced capacity may be ascribed to the increase in the accessibility of the Li ions in the SnOx@Zr-MOF material during cycling, which results in an increased accommodation behavior for lithium.4,54,55 The electrochemical performance of the SnOx-based materials compared to that in the previous studies is shown in Table S1. The greatly enhanced specific capacity, excellent rate capability, and ultrastable cycling ability of the SnOx@Zr-MOFs demonstrate its potential as a promising anode material in LIB applications. To gain insight into the reasons of enhanced electrochemical performance of SnOx@Zr-MOFs, EIS tests of the SnOx@ZrMOF and SnOx electrodes were performed at room temperature (Figure 5e,f). Each spectrum is composed of a semicircle at a high frequency region that is ascribed to the charge transfer resistance (Rct) and an approximately 45° inclined line in the low frequency region corresponding to the Warburg impedance (ZW). ZW is associated with the Li-ion diffusion in the bulk of the electrode materials.56,57 The EIS spectra of the SnOx@ZrMOF and SnOx electrodes were analyzed by the equivalent circuit model shown in Figure S1. Rs and Q represent the Ohmic resistance and constant phase element, respectively. The Zsimpwin software was employed to fit the impedance spectra. EIS fitting showed that the values of Rct for the SnOx and SnOx@Zr-MOF electrodes were 299 and 101 Ω, respectively. The small Rct value accounts for the improved electrochemical performance of the SnOx@Zr-MOF electrode, which means that it has a rapid solid-state diffusion rate of Li ions inside the electrode and a relatively lower electrode/electrolyte interfacial resistance compared to that of the SnOx electrode. Morphological examination of the SnOx@Zr-MOF electrode after 50 cycles was characterized by SEM measurements. As shown in Figure S2, the general morphology of Zr-MOFs retained confirming that it was stable during the Li+ deinsertion process.

the discharge capacities are 1827, 1085, 937, 810, and 650 mA h g−1 from 1st to 5th, respectively. For comparison, capacity and rate performance of pure Zr-MOFs were tested and are exhibited in Figure 5e,f. Obviously, the capacity of the Zr-MOF electrode is negligible compared to that of the SnOx@Zr-MOF electrode (C = 194 mA h g−1). Generally, the large irreversible capacity of SnOx@Zr-MOF (Coulombic efficiency of about 53%) and SnOx (Coulombic efficiency of about 56%) electrodes is mainly ascribed to the SEI layer and the degradation of the electrolyte.49,50 Apart from the first cycle, the Coulombic efficiency of SnOx@Zr-MOFs increases to more than 90%, and the specific capacities are much higher than those of SnOx in the subsequent cycles. Noticeably, the following four cycles discharge and charge curves of the SnOx@ Zr-MOFs electrode almost perfectly overlap and have similar features and tendencies, indicating better cyclic stability capacity retention. As a comparison, the SnOx electrode exhibits a relatively poor reversible process and cyclic stability. The excellent electrochemical performance of the SnOx@ZrMOF anode is attributed to the size of the SnOx nanoparticles and the interaction between the unsaturated Zr4+ sites and the SnOx nanoparticles. The pyrolysis process of the gel polymer is rapid, and the pore diameters of the Zr-MOFs are small, so the formation of the SnOx nanoparticles occurs only on the ZrMOF outer surface. This can also be confirmed by the TEM images in Figure 2e. It is worth noting that the interaction is a vital factor in withstanding the volume expansion and the agglomeration of SnOx nanoparticles during the cycling process. This means that the active substance can be utilized with the highest efficiency in the following cycling process. Therefore, the discharge and charge capacities of the SnOx@ZrMOF electrode are almost the same, whereas that of the SnOx electrode is significantly reduced. In addition, the ultrasmall SnOx nanoparticles can effectively shorten the lithium-ion diffusion distance and improve the electrochemical reaction activity. To further estimate the electrochemical performance of the SnOx@Zr-MOF electrode, the rate performance was also investigated. In Figure 5c, the average discharge capacities of the SnOx@Zr-MOFs are 1336, 1184, 1085, 850, 592, and 358 mA h g−1 at a current density from 50 to 2000 mA g−1, respectively. Remarkably, after the current density finally returns to 50 mA g−1, the discharge-specific capacity successfully recovers to 1135 mA h g−1, 3-fold higher than commercial graphite anode materials. In comparison, the SnOx electrode delivers discharge capacities of 689, 449, 209, 54, 92, and 4 mA h g−1 at a current density from 50 to 2000 mA g−1, respectively. Clearly, the SnOx electrode exhibits a relatively lower rate performance. Most importantly, the performance meets the requirements of electric vehicles and provides a reference for the cutting-edge of Li-ion battery technology because of the superior rate performance and the high specific capacity of the SnOx@Zr-MOF electrode. The cycling performance of the SnOx@Zr-MOF and SnOx anodes was also evaluated by galvanostatic charge−discharge cycling at 50 mA g−1 from 0.01 to 3.0 V for 100 cycles and is shown in Figure 5d. It is observed that SnOx has a high initial capacity but is rapidly attenuated. When the test reached 60 cycles, the capacity decreased from 1872 to 140 mA h g−1 (only 7% retained). In comparison, the SnOx@Zr-MOF shows a more steady property than the SnOx electrode. The capacity of SnOx@Zr-MOFs is about 2192 mA h g−1 in the first cycle. The reversible capacity is about 994 mA h g−1 after 100 cycles. Most

4. CONCLUSIONS SnOx@Zr-MOF composites were successfully produced through Zr-MOF dehydration and nonaqueous sol−gel processes, followed by pyrolysis. The HRTEM examination and elemental mapping indicate that the SnOx nanoparticles were ultrafine with average diameters of about 4 nm and uniformly distributed on the surface of Zr-MOFs without obvious agglomeration. Benefitting from the size of the SnOx nanoparticles and the synergistic effect between SnOx and ZrMOFs, SnOx nanoparticles could accommodate the strain generated during Li intercalation and extraction. This approach could also avoid aggregation of the SnOx nanoparticles and led to an excellent performance (retaining 994 mA h g−1 at 50 mA g−1 after 100 cycles). Notably, the whole synthesis route is convenient in implementation, inexpensive, and time-saving, and the product is stable. Therefore, this work may shed light on the great potential for practical energy applications in LIBs. 35037


Research Article


■

Carbon as High-Performance Anode for Lithium-Ion Batteries. Nano Lett. 2014, 14, 153−157. (14) Li, F.; Du, J.; Yang, H.; Shi, W.; Cheng, P. Nitrogen-DopedCarbon-Coated SnO2 Nanoparticles Derived From a SnO2@MOF Composite as a Lithium Ion Battery Anode Material. RSC Adv. 2017, 7, 20062−20067. (15) 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., Int. Ed. 2007, 119, 764−767. (16) Zhou, X.; Dai, Z.; Liu, S.; Bao, J.; Guo, Y. G. Ultra-Uniform SnOx/Carbon Nanohybrids Toward Advanced Lithium-Ion Battery Anodes. Adv. Mater. 2014, 26, 3943−3949. (17) Sun, S. H.; Meng, G. W.; Zhang, G. X.; Gao, T.; Geng, B. Y.; Zhang, L. D.; Zuo, J. Raman Scattering Study of Rutile SnO2 Nanobelts Synthesized by Thermal Evaporation of Sn Powders. Chem. Phys. Lett. 2003, 376, 103−107. (18) Zhang, L.-S.; Jiang, L. Y.; Yan, H. J.; Wang, W. D.; Wang, W.; Song, W. G.; Guo, Y. G.; Wan, L. J. Mono Dispersed SnO2 Nanoparticles on Both Sides of Single Layer Graphene Sheets as Anode Materials in Li-Ion Batteries. J. Mater. Chem. 2010, 20, 5462. (19) Lin, Z.-J.; Lu, J.; Hong, M.; Cao, R. Metal-Organic Frameworks Based on Flexible Ligands (FL-MOFs): Structures and Applications. Chem. Soc. Rev. 2014, 43, 5867−5895. (20) Li, J.-R.; Sculley, J.; Zhou, H. C. Metal-Organic Frameworks for Separations. Chem. Rev. 2012, 112, 869−932. (21) Zhu, Q.-L.; Xu, Q. Metal-Organic Framework Composites. Chem. Soc. Rev. 2014, 43, 5468−5512. (22) Xia, W.; Mahmood, A.; Zou, R.; Xu, Q. Metal−Organic Frameworks and Their Derived Nanostructures for Electrochemical Energy Storage and Conversion. Energy Environ. Sci. 2015, 8, 1837− 1866. (23) Song, L.; Zhang, J.; Sun, L.; Xu, F.; Li, F.; Zhang, H.; Si, X.; Jiao, C.; Li, Z.; Liu, S.; Liu, Y.; Zhou, H.; Sun, D.; Du, Y.; Cao, Z.; Gabelicai, Z. Mesoporous Metal−Organic Frameworks: Design and Applications. Energy Environ. Sci. 2012, 5, 7508. (24) Li, G.; Yang, H.; Li, F.; Du, J.; Shi, W.; Cheng, P. Facile Formation of a Nanostructured NiP2@C Material for Advanced Lithium-Ion Battery Anode Using Adsorption Property of Metal− Organic Framework. J. Mater. Chem. A 2016, 4, 9593−9599. (25) Sun, Z.; Cao, C.; Han, W. Q. A Scalable Formation of NanoSnO2 Anode Derived from Tin Metal−Organic Frameworks for Lithium-Ion Battery. RSC Adv. 2015, 5, 72825−72829. (26) Wang, M.; Yang, H.; Zhou, X.; Shi, W.; Zhou, Z.; Cheng, P. Rational Design of SnO2@C Nanocomposites for Lithium Ion Batteries by Utilizing Adsorption Properties of MOFs. Chem. Commun. 2016, 52, 717−720. (27) Tan, Y.; Zhang, W.; Gao, Y.; Wu, J.; Tang, B. Facile Synthesis and Supercapacitive Properties of Zr-Metal Organic Frameworks (UiO-66). RSC Adv. 2015, 5, 17601−17605. (28) Niederberger, M. Nonaqueous Sol−Gel Routes to Metal Oxide Nanoparticles. Acc. Chem. Res. 2007, 40, 793−800. (29) Ameloot, R.; Aubrey, M.; Wiers, B. M.; Gomora-Figueroa, A. P.; Patel, S. N.; Balsara, N. P.; Long, J. R. Ionic Conductivity in the MetalOrganic Framework UiO-66 by Dehydration and Insertion of Lithium Tert-Butoxide. Chem. − Eur. J. 2013, 19, 5533−5536. (30) Valenzano, L.; Civalleri, B.; Chavan, S.; Bordiga, S.; Nilsen, M. H.; Jakobsen, S.; Lillerud, K. P.; Lamberti, C. Disclosing the Complex Structure of UiO-66 Metal Organic Framework: A Synergic Combination of Experiment and Theory. Chem. Mater. 2011, 23, 1700−1718. (31) Vermoortele, F.; Ameloot, R.; Vimont, A.; Serre, C.; De Vos, D. An Amino-Modified Zr-Terephthalate Metal-Organic Framework as an Acid-Base Catalyst for Cross-Aldol Condensation. Chem. Commun. 2011, 47, 1521−1523. (32) Vermoortele, F.; Vandichel, M.; Van de Voorde, B.; Ameloot, R.; Waroquier, M.; Van Speybroeck, V.; De Vos, D. E. Electronic Effects of Linker Substitution on Lewis Acid Catalysis with MetalOrganic Frameworks. Angew. Chem., Int. Ed. 2012, 51, 4887−4890.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.7b11620. Equivalent circuit model (Figure S1) and SEM images (Figure S2); electrochemical perfomance (Table S1) (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Bohejin Tang: 0000-0002-1144-3355 Author Contributions †

W.L. and Z.L. contributed equally to this work.

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This project was sponsored by the National Natural Science Foundation of China (11602134) and the Shanghai University of Engineering Science Innovation Fund for Graduate Students (17KY0405).

■

REFERENCES

(1) Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J. M. Li-O2 and Li-S Batteries with High Energy Storage. Nat. Mater. 2011, 11, 19−29. (2) Scrosati, B.; Garche, J. Lithium Batteries: Status, Prospects and Future. J. Power Sources 2010, 195, 2419−2430. (3) Li, Y.; Song, J.; Yang, J. A Review on Structure Model and Energy System Design of Lithium-Ion Battery in Renewable Energy Vehicle. Renewable Sustainable Energy Rev. 2014, 37, 627−633. (4) 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, 2152−2157. (5) Wang, H.; Rogach, A. L. Hierarchical SnO2 Nanostructures: Recent Advances in Design, Synthesis, and Applications. Chem. Mater. 2014, 26, 123−133. (6) Zhou, X.; Yu, L.; Yu, X. Y.; Lou, X. W. D. Encapsulating Sn Nanoparticles in Amorphous Carbon Nanotubes for Enhanced Lithium Storage Properties. Adv. Energy Mater. 2016, 6, No. 1601177. (7) Zhou, X.; Bao, J.; Dai, Z.; Guo, Y. G. Tin Nanoparticles Impregnated in Nitrogen-Doped Graphene for Lithium-Ion Battery Anodes. J. Phys. Chem. C 2013, 117, 25367−25373. (8) 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, 17456. (9) Belliard, F. Novel Tin Oxide-Based Anodes for Li-Ion Batteries. Solid State Ionics 2000, 135, 163−167. (10) Zhang, H.-X.; Feng, C.; Zhai, Y. C.; Jiang, K. L.; Li, Q. Q.; Fan, S. S. Cross-Stacked Carbon Nanotube Sheets Uniformly Loaded with SnO2 Nanoparticles: A Novel Binder-Free and High-Capacity Anode Material for Lithium-Ion Batteries. Adv. Mater. 2009, 21, 2299−2304. (11) Zhang, W.-M.; Hu, J. S.; Guo, Y. G.; Zheng, S. F.; Zhong, L. S.; Song, W. G.; Wan, L. J. Tin-Nanoparticles Encapsulated in Elastic Hollow Carbon Spheres for High-Performance Anode Material in Lithium-Ion Batteries. Adv. Mater. 2008, 20, 1160−1165. (12) Liu, X.; Sun, Q.; Ng, A. M. C.; Djurišić, A. B.; Xie, M.; Dai, B.; Tang, J.; Surya, C.; Liao, C.; Shih, K. An Alumina Stabilized Graphene Oxide Wrapped SnO2 Hollow Sphere LIB Anode with Improved Lithium Storage. RSC Adv. 2015, 5, 100783−100789. (13) Zhu, Z.; Wang, S.; Du, J.; Jin, Q.; Zhang, T.; Cheng, F.; Chen, J. Ultrasmall Sn Nanoparticles Embedded in Nitrogen-Doped Porous 35038


Research Article

ACS Applied Materials & Interfaces (33) Li, J.; Zhu, Q. L.; Xu, Q. Highly Active AuCo Alloy Nanoparticles Encapsulated in the Pores of Metal-Organic Frameworks for Hydrolytic Dehydrogenation of Ammonia Borane. Chem. Commun. 2014, 50, 5899−5901. (34) Wang, Z.; Li, X.; Cui, Y.; Yang, Y.; Pan, H.; Wang, Z.; Wu, C.; Chen, B.; Qian, G. A Metal−Organic Framework with Open Metal Sites for Enhanced Confinement of Sulfur and Lithium−Sulfur Battery of Long Cycling Life. Cryst. Growth Des. 2013, 13, 5116−5120. (35) Wang, B.; Wang, Z.; Cui, Y.; Yang, Y.; Wang, Z.; Qian, G. Electrochemical Properties of SnO2 Nanoparticles Immobilized Within a Metal−Organic Framework as an Anode Material for Lithium-Ion Batteries. RSC Adv. 2015, 5, 84662−84665. (36) Wang, H.; Dou, K.; Teoh, W. Y.; Zhan, Y.; Hung, T. F.; Zhang, F.; Xu, J.; Zhang, R.; Rogach, A. L. Engineering of Facets, Band Structure, and Gas-Sensing Properties of Hierarchical Sn2+-Doped SnO2 Nanostructures. Adv. Funct. Mater. 2013, 23, 4847−4853. (37) Zhang, B.; Yu, Y.; Huang, Z.; He, Y. B.; Jang, D.; Yoon, W. S.; Mai, Y. W.; Kang, F.; Kim, J. K. Exceptional Electrochemical Performance of Freestanding Electrospun Carbon Nanofiber Anodes Containing Ultrafine SnOx Particles. Energy Environ. Sci. 2012, 5, 9895. (38) Liu, H.; Hu, R.; Sun, W.; Zeng, M.; Liu, J.; Yang, L.; Zhu, M. Sn@SnOx/C Nanocomposites Prepared by Oxygen Plasma-Assisted Milling as Cyclic Durable Anodes for Lithium Ion Batteries. J. Power Sources 2013, 242, 114−121. (39) Kumar, R. D.; Karuppuchamy, S. Facile Synthesis of Honeycomb Structured SnO/SnO2 Nanocomposites by Microwave Irradiation Method. J. Mater. Sci.: Mater. Electron. 2015, 26, 6439− 6443. (40) Zhuang, Y.; Seong, J. G.; Do, Y. S.; Jo, H. J.; Cui, Z.; Lee, J.; Lee, Y. M.; Guiver, M. D. Intrinsically Microporous Soluble Polyimides Incorporating Tröger’s Base for Membrane Gas Separation. Macromolecules 2014, 47, 3254−3262. (41) Tonti, D.; Torrallvo, M. J.; Enciso, E.; Sobrados, I.; Sanz, J. Three-Dimensionally Ordered Macroporous Lithium Manganese Oxide for Rechargeable Lithium Batteries. Chem. Mater. 2008, 20, 4783−4790. (42) Aurbach, D.; Nimberger, A.; Markovsky, B.; Levi, E.; Sominski, E.; Gedanken, A. Nanoparticles of SnO Produced by Sonochemistry as Anode Materials for Rechargeable Lithium Batteries. Chem. Mater. 2002, 14, 4155−4163. (43) Chouvin, J.; Branci, C.; Sarradin, J.; Olivier-Fourcade, J.; Jumas, J. C.; Simonb, B.; Biensanb, P. h. Lithium Intercalation in Tin Oxide. J. Power Sources 1999, 81−82, 277−281. (44) Huang, J. Y.; Zhong, L.; Wang, C. M.; Sullivan, J. P.; Xu, W.; Zhang, L. Q.; Mao, S. X.; Hudak, N. S.; Liu, X. H.; Subramanian, A.; Fan, H.; Qi, L.; Kushima, A.; Li, J. In Situ Observation of the Electrochemical Lithiation of a Single SnO2 Nanowire Electrode. Science 2010, 330, 1515−1520. (45) Wang, C.; Zhou, Y.; Ge, M. Y.; Xu, X. B.; Zhang, Z. L.; Jiang, J. Z. Large-Scale Synthesis of SnO2 Nanosheets with High Lithium Storage Capacity. J. Am. Chem. Soc 2010, 132, 46−47. (46) Ding, S.; Luan, D.; Boey, F. Y.; Chen, J. S.; Lou, X. W. SnO2 Nanosheets Grown on Graphene Sheets with Enhanced Lithium Storage Properties. Chem. Commun. 2011, 47, 7155−7157. (47) Lytle, J. C.; Yan, H.; Ergang, N. S.; Smyrl, W. H.; Stein, A. Structural and Electrochemical Properties of Three-Dimensionally Ordered Macroporous Tin(iv) Oxide Films. J. Mater. Chem. 2004, 14, 1616. (48) Li, Z.; Zhang, W.; Tan, Y. Y.; Hu, J. B.; He, S. Y.; Stein, A.; Tang, B. Three-Dimensionally Ordered Macroporous β-Bi2O3 with Enhanced Electrochemical Performance in a Li-ion Battery. Electrochim. Acta 2016, 214, 103−109. (49) Hong, Y. J.; Son, M. Y.; Kang, Y. C. One-Pot Facile Synthesis of Double-Shelled SnO2 Yolk-Shell-Structured Powders by Continuous Process as Anode Materials for Li-Ion Batteries. Adv. Mater. 2013, 25, 2279−2283. (50) Lin, Y.-M.; Abel, P. R.; Flaherty, D. W.; Wu, J.; Stevenson, K. J.; Heller, A.; Mullins, C. B. Morphology Dependence of the Lithium

Storage Capability and Rate Performance of Amorphous TiO2 Electrodes. J. Phys. Chem. C 2011, 115, 2585−2591. (51) Zhu, J.; Lei, D.; Zhang, G.; Li, Q.; Lu, B.; Wang, T. Carbon and Graphene Double Protection Strategy to Improve the SnOx Electrode Performance Anodes for Lithium-Ion Batteries. Nanoscale 2013, 5, 5499−5505. (52) Zhang, B.; Huang, J.; Kim, J. K. Ultrafine Amorphous SnOx Embedded in Carbon Nanofiber/Carbon Nanotube Composites for Li-Ion and Na-Ion Batteries. Adv. Funct. Mater. 2015, 25, 5222−5228. (53) Hou, X.; Hu, Y.; Jiang, H.; Li, Y.; Li, W.; Li, C. One-Step Synthesis of SnOx Nanocrystalline Aggregates Encapsulated by Amorphous TiO2 as an Anode in Li-Ion Battery. J. Mater. Chem. A 2015, 3, 9982−9988. (54) Wu, Z.-S.; Sun, Y.; Tan, Y. Z.; Yang, S.; Feng, X.; Mullen, K. Three-Dimensional Graphene-Based Macro- and Mesoporous Frameworks for High-Performance Electrochemical Capacitive Energy Storage. J. Am. Chem. Soc. 2012, 134, 19532−19535. (55) Wu, H.; Yu, G.; Pan, L.; Liu, N.; McDowell, M. T.; Bao, Z.; Cui, Y. Stable Li-ion Battery Anodes by In-Situ Polymerization of Conducting Hydrogel to Conformally Coat Silicon Nanoparticles. Nat. Commun. 2013, 4, No. 2941. (56) Ko, Y. N.; Park, S. B.; Jung, K. Y.; Kang, Y. C. One-Pot Facile Synthesis of Ant-Cave-Structured Metal Oxide-Carbon Microballs by Continuous Process for Use as Anode Materials in Li-Ion Batteries. Nano Lett. 2013, 13, 5462−5466. (57) Wang, B.; Su, D. W.; Park, J.; Ahn, H.; Wang, G. X. GrapheneSupported SnO2 Nanoparticles Prepared by a Solvothermal Approach for an Enhanced Electrochemical Performance in Lithium-Ion Batteries. Nanoscale Res. Lett. 2012, 7, 215−221.

35039


Synthesis and Electrochemical Performance of SnOx Quantum Dots

Recommend Documents