One-Dimensional YolkâShell Sb@TiâOâP ... - ACS Publications

Subscriber access provided by UB + Fachbibliothek Chemie | (FU-Bibliothekssystem)

Article

One-Dimensional Yolk-Shell Sb@Ti-O-P Nanostructures as a HighCapacity and High-Rate Anode Material for Sodium Ion Batteries Nana Wang, Zhongchao Bai, Yitai Qian, and Jian Yang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b13193 • Publication Date (Web): 16 Dec 2016 Downloaded from http://pubs.acs.org on December 17, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

One-Dimensional Yolk-Shell Sb@Ti-O-P Nanostructures as a High-Capacity and High-Rate Anode Material for Sodium Ion Batteries Nana Wang,ab Zhongchao Bai,b Yitai Qian,ac Jian Yang a* a

Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, School of

Chemistry and Chemical Engineering Shandong University, Jinan 250100, PRC,

b

Research

Institute of Surface Engineering, Taiyuan University of Technology, Taiyuan, 030024, PRC,

c

Hefei National Laboratory for Physical Science at Microscale, Department of Chemistry, University of Science and Technology of China, Hefei, 230026, PRC Keywords: antimony; composite; nanostructures; sodium ion batteries; full cells

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 26

Abstract: Development of high energy/power density and long cycle life of anode materials is highly desirable for sodium ion batteries, because graphite anode cannot be used directly. Sb stands out from the potential candidates, due to high capacity, good electronic conductivity and moderate sodiation voltage. Here, one-dimensional yolk-shell Sb@Ti-O-P nanostructures are synthesized by reducing core-shell Sb2O3@TiO2 nanorods with NaH2PO2. This structure has Sb nanorod as the core to increase the capacity, and Ti-O-P as the shell to stabilize the interface between electrolyte and electrode material. The gap between the core and the shell accommodates the volume change during sodiation/desodiation. These features endow the structure outstanding performances. It could deliver a capacity about 760 mAh g-1 after 200 cycles at 500 mA g-1, with a capacity retention about 94%. Even at 10 A g-1, the reversible capacity is still at 360 mAh g-1. The full battery of Sb@Ti-O-P//Na3V2(PO4)3-C presents a high output voltage (~ 2.7 V) and a capacity of 392 mAh g-1anode after 150 cycles at 1 A g-1anode.


2

Page 3 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Introduction Lithium ion batteries (LIBs) have been successfully commercialized in the past decades and extensively integrated into portable electronics, automobiles and hybrid electric vehicles. However, the unevenly distributed resources and low abundance of lithium in earth could not satisfy the growing consumption.1,2 Recently, sodium ion batteries (NIBs) have gained significant attention as an ideal alternative to LIBs to address these concerns. But the commercialized anode for LIBs, graphite, does not work for NIBs, because its interlayer distance is not large enough to hold Na ions due to their large cation radii (1.02 Å).3 The similar case also happens to silicon.4 Thus, many efforts have been devoted to seek after alternative materials. As a result, a number of candidates start to come into sight, including metal sulfides, metal oxides, organic polymers, metallic alloys.1,5-7 In these candidates, Sb stands out from the rest, due to its high theoretical capacity (~ 660 mAh g-1), good electronic conductivity, and moderate sodiation voltage. But the big volume change during sodiation/desodiation processes, which could cause structure fracture and lead to inferior electronic conductivity and poor cycling stability, degrades its performances as the anode material. This case is also encountered in the alloy-type anode materials of LIBs. So, the solutions to this issue could be borrowed for NIBs, including size/shape control (nanoparticles, nanorods),8,9 structure engineering (nanotubes, nanorod arrays, hollow nanospheres),10-14 surface modification (carbon, TiO2, or Sb2O3 coating),12-15 and component modulation (Sb/graphene, Sb/MWCNT, Cu2Sb, ZnSb).16-20 These strategies have remarkably enhanced the performances of Sb. In spite of this, there are still many challenges in the front of the application. For instances, the porous structure, which is well known for its enhancement on cycling stability and rate capability, also reduces the packing density and decreases the initial coulombic efficiency due to the large specific surface area. Recently reported Sb/TiO2-x nanotubes and Sb/C


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 26

nanotubes are typical examples in this regard.12,13 Although they exhibit outstanding electrochemical performances, the initial coulombic efficiency was only ~65 % for Sb/TiO2-x and 50.6 % for Sb/C. Moreover, the empty interior is more than enough to fit the volume change, resulting in the space waste. Meanwhile, the materials used to stabilize the interface between electrolyte and electrode materials, which are carbon or TiO2 in most cases, have very limited capacity and greatly lower the composite capacity. Thus, how to design the hollow structure with a high space efficiency, and achieve the stable surface without the cost of composite capacity, is a great challenge to us. Here, one-dimensional yolk-shell Sb@Ti-O-P nanostructures are synthesized by the reduction of core-shell Sb2O3@TiO2 nanorods with NaH2PO2 at a low temperature. As accompanied by the reduction of Sb2O3 and TiO2, phosphorus is anchored in the shell via the formation of P-O bonds, generating the unique Ti-O-P shell. This yolk-shell structure well addresses the above concerns, because the empty interior is occupied by high-capacity Sb nanorods. Meanwhile, the Ti-O-P shell offers a robust and stable surface between electrolyte and electrode material. The gap between the Sb nanorod and the Ti-O-P shell benefits the releasing of the strain/stress induced by the volume change, and improves the space efficiency. What’s more, the surface oxidation of the Sb nanorods increases the composite capacity. To our knowledge, such a Sb-based structure has not been reported before. As expected, this structure delivers improved specific capacity, and outstanding rate capability. It could stay at 760 mAh g-1 after 200 cycles at 500 mA g-1. Even at 10 A g-1, the capacity is still kept at 360 mAh g-1. The initial coulombic efficiency could be promoted to 75.0 %. After matched with Na3V2(PO4)3/C for a full cell,21 this structure exhibits a high output voltage and a high capacity.


4

Page 5 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Results and Discussion The synthesis of yolk-shell Sb@Ti-O-P nanostructures is briefly presented in Scheme 1. First, high-quality Sb2O3 nanorods with their lengths up to hundreds of micrometers were obtained by a simple and efficient process at room temperature (Figure S1). Then, an amorphous TiO2 layer was coated on the surface of these nanorods via a controlled hydrolysis of TBOT (Figure S2). As the core-shell Sb2O3@TiO2 nanorods were heated with NaH2PO2 together, NaH2PO2 underwent the disproportionation, releasing gaseous and reductive PH3.22 Sb2O3 was reduced to metallic Sb that gradually shrinked and detached from the TiO2 shell. Such a yolk-shell structure facilitates the anode material to keep its stability during repeated sodiation/desodiation processes.23,24 Meanwhile, TiO2 was partially reduced, introducing Ti3+ and oxygen vacancies into the shell. The formation of oxygen-deficient TiO2-x could effectively improve the electron conductivity and the charge-transfer kinetics,13,25,26 promoting the electrochemical performances. The oxidation product of PH3 is likely to be fixed on the surface or the subsurface via the formation of P-O. Thus, the final product could be denoted as yolk-shell Sb@Ti-O-P.

Scheme 1. The formation process of one-dimensional yolk-shell Sb@Ti-O-P nanostructures.


5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 26

Figure 1. (a) XRD pattern, (b) EDX spectra, (c) survey spectra and (d-f) high-resolution spectra of Sb 3d, Ti 2p and P 2p in Sb@Ti-O-P. Figure 1a shows the XRD pattern of Sb@Ti-O-P. All the diffraction peaks can be indexed as rhombohedral-phase Sb (JCPDS Card, No, 35-0732). No diffraction peaks belonging to Ti/POx are observed in the pattern, indicating their poor crystallinity. In spite of this, EDS spectra clearly confirm the existence of Ti and P in the product (Figure 1b). This result is also supported by the XPS spectrum of Sb@Ti-O-P, in which the signals of Sb 3d, Ti 2p and P 2p are easily observed (Figure 1c). The high-resolution spectra of these signals were measured to gain insights about their valence status. As shown in Figure 1d, the high-resolution spectrum of Sb 3d consists of two doublets, but they have to be deconvoluted into five peaks in view of the overlapping of Sb 3d5/2 in Sb2O3 with O 1s. The peaks at 527.9 and 537.3 eV could be ascribed to Sb 3d5/2 and 3d3/2 from metallic Sb.27 The peaks at 531.0 and 540.4 eV could be attributed to Sb 3d5/2 and 3d3/2 from SbOx.27 Because the peak intensities of SbOx are much higher than those from metallic Sb, it indicates that there is severe surface oxidation on the product. In order to confirm


6

Page 7 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


this point, Ar-ion sputtering was conducted to remove the surface layer. As presented in Figure 1d, the peak intensities of metallic Sb greatly increase, showing a higher ratio of Sb0/Sb3+ relative to the data before the sputtering. This result suggests that metallic Sb basically locates at the core, and its surface is oxidized, which might be caused by the storage in air. The case of Ti 2p is different from that of Sb 3d. There is no metallic Ti in the product, although the fitting of Ti 2p also shows two doublets (Figure 1e). The doublet at 459.9 and 465.6 eV is believed to come from Ti 2p3/2 and Ti 2p1/2 of Ti4+-O-P.28-30 The other at 458.8 and 464.5 eV is consistent with Ti 2p3/2 and Ti 2p1/2 of Ti4+-O.28-30 After the removal of the surface layer, the doublet of Ti3+ species at 457.5 and 462.9 eV appears in the product. This result indicates the similar surface oxidation for Ti species. Different from the cases of Ti 2p and Sb 3d, there is no apparent change for P 2p before and after the Ar-ion sputtering (Figure 1f). The two peaks at 133.9 and 134.4 eV are in line with the data of P-O bonds.28-30 It is noted that the ratios of P/Ti and Ti/Sb after Ar-ion sputtering greatly decrease, consistent with their unique structure as illustrated in Scheme 1. Figure 2a shows a typical SEM image of Sb@Ti-O-P, where the one-dimensional structure of Sb2O3 is well retained after the controlled hydrolysis for the TiO2 shell and the low-temperature heating for Sb and Ti-O-P. The high-magnification SEM image on the tip of these structures (Figure 2b) shows a nanorod at the core detached from the external shell, as highlighted by the red circles. Such a yolk-shell structure is in a high yield in the product, because this feature could be visualized on most of the particles. This result is also supported by TEM images. As shown in Figure 2c, there is a significant gap between the shell and the core, well consistent with the yolkshell structure. The careful observation further discloses that the nanorod contains multiple pores with their sizes in tens of nanometers, which agrees well with the pore size distribution obtained from nitrogen sorption isotherms (Figure S3). The formation of the pores likely comes from the


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 26

Figure 2. (a, b) SEM images, (c) TEM image, (d, e) HRTEM images, (f) elemental mapping images, and (g) line scanning profiles of Sb@Ti-O-P. escape of gaseous H2O produced by the reduction of Sb2O3. The HRTEM image on the shell presents distorted and dim lattice fringes from anatase TiO2 (Figure 2d), confirming its poor crystallinity again. The HRTEM image on the core nanorod shows clear lattice fringes with the spacing about 0.31 nm (Figure 2e), corresponding to (012) planes of metallic Sb. However, we


8

Page 9 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


cannot observe the lattice fringes from any potential compounds that contain phosphorus, no matter at the core or in the shell. Thus, element mapping and line scanning were conducted to disclose its distribution in the yolk-shell structure. As illustrated in Figure 2g-2f, metallic Sb basically locates at the core, and Ti, O, and P distribute on the shell, forming a yolk-shell Sb@ Ti-O-P structure.

Figure 3. The effects of binders or electrolytes on the cycling performance of Sb@Ti-O-P. The current density was 100 mA g-1. Figure 3 presents the influences of electrolytes (EC/DEC or PC) and binders (CMCNa or PANa) on the electrochemical properties, prior to the detailed electrochemical measurements. It is found that Sb@Ti-O-P exhibits the best performances with PANa as the binder and PC as the electrolyte, which could be attributed to the formation of a uniform and dense layer on active materials.31,32 The first discharge/charge capacity is 1092.5/819.7 mAh g-1, resulting in an initial coulombic efficiency about 75.0%. The capacity loss may be attributed to the decomposition of electrolyte, the formation of a polymeric gel-like film, irreversible sodium storage either on the surface or inside the nanopores.3,34,35 The specific capacity after 80 cycles at 100 mA g-1 is ~ 750 mAh g-1, is much higher than the theoretical data calculated by the weight percentage of Sb and


9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 26

TiO2 (564.85 mAh g-1 = 660 mAh g-1 * 80 wt% + 335 mAh g-1 * 11 wt %). Even if the contributions of carbon and binder are taken into accounts (Figure S4), they still do not fill the gap between theoretical capacity and experiment data. So, it is concluded that other components must participate the electrochemical reactions. Sb2O3 on the surface of Sb attracts our attention, because it exhibits a theoretical capacity as high as 1103 mAh g-1. Furthermore, the conversion reaction of Sb/Sb2O3 at ~1.2 V in the anodic sweep and ~1.6 V in the cathodic sweep,35,36 is in good agreement with what observed in CV curves of Sb@Ti-O-P (the inset of Figure 4a). Because these peaks are broad and weak, they are easy to be neglected or covered by other peaks. To directly confirm the reversible reaction between Sb2O3 and Sb, Sb/Sb2O3 nanoparticles were prepared (Figure S5a) and tested between 0.02-2.5 V (Figure S5b). After the first discharge, the products charged to 1.5 V and 2.5 V were taken for HRTEM images. As shown in Figure S5c, the product charged to 1.5 V is composed by metallic Sb and Na2O. But that charged to 2.5 V is identified as Sb2O3 (Figure S5d). These results indicate that Sb could be further oxidized to Sb2O3 at a high voltage, thus improving the capacity. In view of the excellent performance of Sb@Ti-O-P in PANa/PC, the following tests are conducted with PANa as the binder and PC as the electrolyte. The CV curves of Sb@Ti-O-P for the first six cycles are shown in Figure 4a. The first cathodic sweep shows two peaks, a broad and weak peak at 1.10 V and an intense peak at 0.37 V. The former could be associated with the decomposition of the electrolyte, the formation of a solid-electrolyte interphase (SEI) layer and the reduction of Sb2O3 on the surface.35,36 The latter originates from the sodiation processes of Sb.8,37 The intercalation of Na+ into TiO2 occurs over a wide range from 1.5 to 0.5 V (Figure S6), which might be covered by the above reactions. In the first anodic sweep, the broad peak could be fitted by three peaks (0.86 V, 1.08 V, 1.40 V), which


10

Page 11 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


likely comes from the desodiation processes of NaxSb and NaxTiO2,8,35-37 and the further oxidetion of Sb to SbOx.35,36 Because of the close voltages, they overlap with each other, resulting in a tailing peak. In the second sweep, the cathodic peak at 1.30 V and the anodic peak tailing above 1.5 V could be still observed, indicating the conversion reaction between Sb and Sb2O3. From then on, CV curves overlap very well, indicating the good reversibility. Figure 4b shows the cycling performances of Sb@Ti-O-P, Sb nanoparticles (Figure S7), TiO2-x (Figure S8), and

Figure 4. (a) Cyclic voltammograms of Sb@Ti-O-P. (b) cycling performances, and (c) rate performances of Sb@Ti-O-P, Sb, TiO2-x and P. The cycling test was conducted at 500 mA g-1. (d) The comparison of the rate performances between Sb@Ti-O-P and the reported works.


11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 26

commercial P powders (Figure S9) at the same current density of 500 mA g-1. In these materials, P powders show the highest sodiation capacity for the first cycle, ~ 2000 mAh g-1. But its first desodiation capacity drops to ~ 600 mAh g-1, suggesting a very low coulombic efficiency. The capacity quickly falls to ~70 mAh g-1 after 60 cycles, indicating the poor cycling stability. Compared to the case of P powders, Sb nanoparticles are much better in terms of cycling stability, although they also show the obvious degradation after 200 cycles. TiO2-x exhibits the excellent stability throughout the cycling, but its capacity is very limited, ~ 140 mAh g-1. Besides these materials, Sb/TiO2 microtubes obtained by the calcination of Sb2O3@TiO2 at 500 oC in Ar/H2 (Figure S10) are also tested, because they combine the high capacity of Sb with high stability TiO2 in one structure. As expected, they show a decent capacity (~ 300 mAh g-1) and an enhanced stability, but these terms are still worse than those of Sb@Ti-O-P. Sb@Ti-O-P exhibits the superior performances in terms of both reversible capacity and cycling stability, much better than the individual component alone. Sb@Ti-O-P could maintain a capacity of 760 mAh g-1 after 200 cycles with a capacity retention about 94%. The cycled electrode basically keeps the onedimensional structure of Sb@Ti-O-P, confirming the structure stability (Figure S11). The similar conclusions could be also achieved from the rate performances. As shown in Figure 4c, Sb@TiO-P displays the excellent reversibility at high rates. Its specific capacity could be preserved at 805, 730, 680, 605, 510, 420, 360 mAh g-1 at the current density of 0.1, 0.2, 0.5, 1, 2, 5 and 10 A g-1, much higher than the individual component alone. Such a rate performance is much better than those of Sb-based anodes in the previous works, as listed in Figure 4d.11-16,38-46 These works include the well-designed Sb nanostructures like hollow Sb microspheres (313 mAh g-1 at 3.2 A g-1),11 nanoporous Sb powders (420 mAh g-1 at 3.3 A g-1),38 etc., the diverse Sb/C composites like Sb/reduced graphene oxides (192 mAh g-1 at 3.3 A g-1),39 Sb/C nanofibers (337


12

Page 13 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


mAh g-1 at 3 A g-1),14 and Sb/C nanosheets (142 mAh g-1 at 10.0 A g-1),40 etc., and MSb alloys like hollow SbNi nanospheres (300 mAh g-1 at 3.3 A g-1),16 Zn4Sb3 nanowires (187 mAh g-1 at 2.07 A g-1),41 etc.. Moreover, the performance of our composite is also superior to many P-based anodes, like amorphous red phosphorus confined in mesoporous carbon matrix (CMK-3) (227 mAh g-1 at 8.0 A g-1, 9.8 C),47 red phosphorus entangled with single-walled carbon nanotubes (300 mAh g-1 at 2.0 A g-1),36 etc.

Figure 5. (a) Discharge/charge curves of Sb@Ti-O-P at different rates, (b) Cycling performance and coulombic efficiency of Sb@Ti-O-P at 3 A g-1. (c) Schematic illustration on the sodiation/ desodiation process of Sb@Ti-O-P. The charge-discharge curves of Sb@Ti-O-P at different rates are shown in Figure 5a. The discharge plateau was at ~ 0.7-0.3 V versus Na/Na+, which could prevent the formation of sodium dendrites and alleviate the safety risks. At the same time, this plateau also ensures the


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 26

full cell based on this anode a high energy density. The cycling performance at a high current density was also evaluated in Figure 5b. Sb@Ti-O-P demonstrates an initial coulombic efficiency about 72% and maintains above 99% in the subsequent cycles. After cycled at 3 A g-1 for 300 times, it still preserves a capacity of 346 mAh g-1, corresponding to a capacity retention of 88%. The excellent electrochemical properties of Sb@Ti-O-P could be associated with the effective cooperation of multiple components in a favorable structure. Metallic Sb is present as the core to enhance the charge-transfer kinetics. Meanwhile, Sb has a fair theoretical capacity (~ 660 mAh g-1). Although this data is not comparable to that of phosphorus, it is higher than many anode materials (TiO2: 330 mAh g-1, carbon: ~300 mAh g-1).48 Ti-O-P is present here as the shell to construct a stable surface with the electrolyte. Meanwhile, the self-doping of Ti3+ in TiO2 promotes the electron conductivity. On the other hand, the yolk-shell structure assembled by these components as Sb@Ti-O-P, effectively tolerates the volume change upon cycling and make the structure stable. This result is briefly depicted in Figure 5c. All these features, not only from the component itself, but also from their combination mode, make the composite excellent in sodium storage in terms of cycling stability and rate capability.

Figure 6. (a) Cycling performance and coulombic efficiency and (b) Charge/discharge curves of Sb@Ti-O-P//Na3V2(PO4)3-C full battery.


14

Page 15 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Inspired by the excellent performance of Sb@Ti-O-P in half cells, the full cells with Na3V2(PO4)3/C as a cathode (Figure S12) have been assembled and tested. Figure 6a presents the cycling performance of the full cell within 1.2-3.8 V at a current density of 1 A g-1anode. After 150 cycles, the cell still preserves a discharge capacity of 392 mAh g-1anode and a high coulombic efficiency (> 98%). The capacity loss in the first several cycles can be ascribed to the SEI film formation and partly irreversible utilization of Na+ by Na3V2(PO4)3/C cathode. Figure 6b displays the charge-discharge curves of the full cell at different current densities. The cell could display the capacity of 737, 627, 536, 483, 423, 382 mAh g-1anode at 0.1, 0.2, 0.5, 1, 2 and 5 A g1

anode.

As the current densities increase from 0.1 A g-1anode to 5 A g-1anode, the output voltage

decreases from 2.72 V to 2.65 V, due to the polarization of anode component and cycling at large current densities. Compared to the previous reports about Na-ion full batteries (Na3V2(PO4)3// MoO3: 1.4 V, 164 mAh g-1anode after 14 cycles,49 Na3V2(PO4)3//FeSe2: 1.7 V, 298 mAh g-1anode after 150 cycles at 1 A g-1anode,5 and Na0.8Ni0.4Ti0.6O2//Na0.8Ni0.4Ti0.6O2: 2.8 V, 85 mAh g-1 anode after 150 cycles at 100 mA g-1anode),50 the output voltage and cycling capacity have been improved a lot by Sb@Ti-O-P//Na3V2(PO4)3/C, indicating the promising potential for it to be used in sodium ion batteries. Conclusions In summary, one-dimensional yolk-shell nanostructure of Sb@Ti-O-P, has been successfully synthesized via a simple process. Because this structure is not airtight, the surface of Sb nanorod at the core is oxidized, due to the exposure to air. The similar surface oxidation also happens to Ti and P at the shell, reducing the content of Ti3+ species and resulting in the formation of P-O. In spite of this, Sb@Ti-O-P still shows excellent electrochemical performances. It presents a capacity of 760 mAh g-1 after 200 cycles at a current density of 500 mA g-1, corresponding to a


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 26

capacity retention about 94% relative to the first charge capacity. Even at 3 A g-1 for 300 cycles, the capacity levels off at 346 mAh g-1. Its high rate capability is also confirmed by 360 mAh g-1 at 10 A g-1. All these results are much better than the individual components alone. Sb@Ti-O-P, paired with Na3V2(PO4)3/C as a full cell, could reach a capacity of 392 mAh g-1anode after 150 cycles at 1 A g-1anode, disclosing its promising potential in the practical applications. These superior performances could be attributed to the good electronic conductivity of Sb, stable cycling stability of TiO2 in Ti-O-P, and the participation of Sb2O3 in sodiation/desodiation. Meanwhile, the unique yolk-shell structure benefits the releasing of interior strain and stress, and keeps the structure stable. It is believed that this method offers a new pathway to fabricate highcapacity and long-lived anode materials for sodium ion batteries. Experimental Section Synthesis of Sb2O3@TiO2: Antimony (Sb) powders (18µm, 120 mg) were stirred in an aqueous solution containing poly(vinylpyrrolidone) (PVP, MW 58000, 400 mg) and ethylenediamine (EDA, 9 mmol) at 25 oC for 16 h. The white precipitation was filtrated and dried in vacuum at 60 o

C to get Sb2O3 nanorods. Then, Sb2O3 nanorods (120 mg) and ammonia (0.2 mL, 28 wt%) were

added into ethanol (40 mL). After the dispersion was treated by ultrasound for 30 min, tetrabutyl titanate (TBOT, 0.4 mL) was added dropwise. The solution was stirred at 45 oC for 10 h. The resultant product, Sb2O3@TiO2 nanorods, was filtrated and washed with ethanol for three times. Synthesis of Sb@Ti-O-P: NaH2PO2 and Sb2O3@TiO2 were placed into two ceramic boats. The boat with Sb2O3@TiO2 was at the downstream inside the furnace. The weight ratio of NaH2PO2 to Sb2O3@TiO2 was controlled at 6:0.1. Then, they were kept at 280 oC in Ar for 2 h. After cooled to room temperature, the black product was collected for structure characterization and electrochemical measurements.


16

Page 17 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Material characterization: Crystal structure of the products was characterized by X-ray diffracttometer equipped with a graphite monochromator (Cu Kα radiation, λ =1.5418 Å, Bruker D8 Adv, Germany). Size and morphology of the products was pictured by field-emission scanning electron microscope (SEM, SUPRATM 55, Germany), transmission electron microscope (TEM, JEOL JEM 1011, Japan), and high resolution transmission electron microscope (HRTEM, JEOL 2100, Japan). Thermal gravimetric (TG) analysis was performed on a thermal analyzer (Mettler Toledo TGA/ SDTA851, Switzerland). X-ray photoelectron spectra (XPS) were acquired from X-ray photoelectron spectrometer (ESCALAB 250, USA) to identify the chemical components and their valences. Electrochemical measurements: The working electrode was made from active material (70 wt%), conductive carbon black (20 wt%), and sodium polyacrylate (PANa, 10 wt%) or sodium carboxyl methyl cellulose (CMCNa, 10 wt%) dispersed in droplets of distilled water. The asformed slurry was sonicated at room temperature for half an hour. Then, it was spread over a copper foil cleaned by ethanol for several times. After dried in vacuum at 60 oC for 12 h, the copper foil was punched into discs with a mass loading about ~ 1 mg cm-2. The working electrode was assembled with metallic sodium as the anode, and glass microfibers of Whatman GF/F as the separator into coin cells (2032) in a glove box full of argon (Mikrouna, Super 1220/750/900). The electrolyte was either 1.0 M NaClO4 in propylene carbonate (PC) or 1.0 M NaClO4 in ethylene carbonate (EC) and diethyl carbonate (DEC) (1:1 vol.) containing 3.5 % (vol.) of fluoroethylene carbonate (FEC). Glavanostatic discharge-charge cycling was conducted on battery cyclers (Land- CT2001A, China). Here, the current density and the reversible capacity are reported based on the total weight of Sb@Ti-O-P composite, unless specifically notified. Cyclic voltammetry (CV) were carried out on electrochemical workstations (LK 2005A, China)


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 26

with a scanning rate of 0.1 mV s-1. For the Na-ion full cell, home-made Na3V2(PO4)3/C17, acetylene black and polyvinylidene fluoride (PVDF) in a weight ratio of 75: 15: 10, were used to fabricate the cathode using Al foil as the current collector.22 Before the use in the full cell, the anode was electrochemically activated for three cycles to eliminate the huge capacity loss in the first cycle. For the full cells, the voltage cutoff window was 1.0-3.8 V, and the excess capacity of cathode is controlled at ~ 10% while the anode is limited. Supporting information XRD pattern and SEM images of Sb2O3 and Sb2O3@TiO2 nanorods; nitrogen sorption isotherm of Sb@Ti-O-P; Cycling performances of carbon, binder and Sb2O3; XRD pattern and discharge/ charge profiles of Sb/Sb2O3 nanoparticles; HRTEM images of Sb/Sb2O3 nanoparticles charged to 1.5 V and 2.5 V after the first discharge; CV curves of anatase TiO2; XRD pattern and TEM image of Sb nanocrystals; TEM images of TiO2 and P particles; Cycling performance of P particles; SEM and TEM images of cycled Sb@Ti-O-P; XRD pattern, TEM image, chargedischarge curves and cycling performance of Na3V2(PO4)3/C. These materials are available free of charge via the Internet at http://pubs.acs.org. Corresponding Author Professor Jian Yang, E-mail: [email protected] Tel.: +86 531 88364489 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.


18

Page 19 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Acknowledgments This work was supported by National Nature Science Foundation of China (Grant No. 51172076, 21471090, 61527809), Shandong Provincial Natural Science Foundation for Distinguished Young Scholar (JQ201205), and Taishan Scholarship in Shandong Province (ts201511004). References [1] Yabuuchi, N.; Kubota, K.; Dahbi, M.; Komaba, S. Research Development on Sodium-Ion Batteries. Chem. Rev. 2014, 114, 11636-11682. [2] Massé, R. C.; Uchaker, E.; Cao, G. Beyond Li-Ion: Electrode Materials for Sodium-and Magnesium-Ion Batteries. Sci. China Mater. 2015, 58, 715-766. [3] Stevens, D. A.; Dahn, J. R. The Mechanisms of Lithium and Sodium Insertion in Carbon Materials. J. Electrochem. Soc. 2011, 148, A803-A811. [4] Sangster, J.; Pelton. A. D. The Na-Si (Sodium-Silicon) System. J. Phase Equilib. 1992, 13, 67-69. [5] Zhang, K.; Hu, Z.; Liu, X.; Tao, Z.; Chen, J. FeSe2 Microspheres as a High-Performance Anode Material for Na-Ion Batteries, Adv. Mater. 2015, 27, 3305-3309. [6] Zhang, Y.; Zhu, P.; Huang, L.; Xie, J.; Zhang, S.; Cao, G.; Zhao, X. Few-Layered SnS2 on Few-Layered Reduced Graphene Oxide as Na-Ion Battery Anode with Ultralong Cycle Life and Superior Rate Capability. Adv. Funct. Mater. 2015, 25, 48-489. [7] Zhao, R.; Zhu, L.; Cao, Y.; Ai, X.; Yang, H. X. An Aniline-Nitroaniline Copolymer as a High Capacity Cathode for Na-Ion Batteries. Electrochem. Commun. 2012, 21, 36-38. [8] He, M.; Kravchyk, K.; Walter, M.; Kovalenko, M. V. Monodisperse Antimony Nanocrystals for High-Rate Li-ion and Na-ion Battery Anodes: Nano versus Bulk. Nano Lett. 2014, 14, 12551262.


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 26

[9] Li, Z.; Tan, X.; Li, P.; Kalisvaart, P.; Janish, M. T.; Mook, W. M.; Luber, E. J.; Jungjohann, K. L.; Carter, C. B.; Mitlin, D. Coupling in Situ TEM and Ex Situ Analysis to Understand Heterogeneous Sodiation of Antimony. Nano Lett. 2015, 15, 6339-6348. [10] Liang, L.; Xu, Y.; Wang, C.; Wen, L.; Fang, Y.; Mi, Y.; Zhou, M.; Zhao, H.; Lei, Y. Largescale Highly Ordered Sb Nanorod Arrays Anode with High Capacity and Rate Capability for Sodium-Ion Batteries. Energy Environ. Sci. 2015, 8, 2954-2962. [11] Hou, H.; Jing, M.; Yang, Y.; Zhang, Y.; Zhu, Y.; Song, W.; Yang, X.; Ji, X. Sb Porous Hollow Microspheres as Advanced Anode Materials for Sodium-Ion Batteries. J. Mater. Chem. A 2015, 3, 2971-2977. [12] Liu, Z.; Yu, X-Y.; Lou, X.; Paik, U. Sb@C Coaxial Nanotubes as a Superior Long-Life and High-Rate Anode for Sodium Ion Batteries. Energy Environ. Sci. 2016, 9, 2314-2318. [13] Wang, N.; Bai, Z.; Qian, Y.; Yang, J. Double-Walled Sb@TiO2−x Nanotubes as a Superior High-Rate and Ultralong-Lifespan Anode Material for Na-Ion and Li-Ion Batteries. Adv. Mater. 2016, 28, 4126–4133. [14] Wu, L.; Hu, X.; Qian, J.; Pei, F.; Wu, F.; Mao, R.; Ai, X.; Yang, H.; Cao, Y. Sb-C Nanofibers with Long Cycle Life as an Anode Material for High-Performance Sodium-Ion Batteries. Energy Environ. Sci. 2014, 7, 323-328. [15] Nam, D.-H.; Hong, K.-S.; Lim, S.-J.; Kim, M.-J.; Kwon, H.-S. High-Performance Sb/Sb2O3 Anode Materials Using a Polypyrrole Nanowire Network for Na-Ion Batteries. Small 2015, 11, 2885-2892. [16] Liu, J.; Yang, Z.; Wang, J.; Gu, L.; Maier, J.; Yu, Y. Graphene-Protected 3D Sb-based Anodes Fabricated via Electrostatic Assembly and Confinement Replacement for Enhanced Lithium and Sodium Storage. Nano Energy 2015, 16, 389-398.


20

Page 21 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


[17] Hu, L.; Zhu, X.; Du, Y.; Li, Y.; Zhou, X.; Bao, J. A Chemically Coupled Antimony/ Multilayer Graphene Hybrid as a High-Performance Anode for Sodium-Ion Batteries. Chem. Mater. 2015, 27, 8138-8145. [18] Zhou, X.; Dai, Z.; Bao, J.; Y-G, Guo. Wet Milled synthesis of Sb/MWCNT Nanocomposite for Improved Sodium Storage. J. Mater. Chem. A 2013, 1, 13727-13731. [19] Baggetto, L.; Allcorn, E.; Manthiram, A.; Veith, G. M. Cu2SbThin Films as Anode for NaIon Batteries. Electrochem. Commun. 2013, 27, 168-171. [20] Liao, S.; Sun, Y.; Wang, J.; Cui, H.; Wang, C. Three Dimensional Self-Assembly ZnSb Nanowire Balls with Good Performance as Sodium Ions Battery Anode. Electrochim. Acta 2016, 211, 11-17. [21] Li, G.; Jiang, D.; Wang, H.; Lan, X.; Zhong, H.; Jiang, Y. Glucose-Assisted Synthesis of Na3V2(PO4)3/C Composite as an Electrode Material for High-Performance Sodium-Ion Batteries. J. Power Sources 2014, 265, 325-334. [22] Guan, Q.; Li, W. A Novel Synthetic Approach to Synthesizing Bulk and Supported Metal Phosphides. J. Catal. 2010, 271, 413-415. [23] Wang, Y.-X.; Yang, J.; Chou, S.-L.; Liu, H.; Zhang, W.-X.; Zhao, D.; Dou, S. Uniform Yolk-Shell Iron Sulfide-Carbon Nanospheres for Superior Sodium–Iron Sulfide Batteries, Nature Commun. 2015, 6, 8689-8698. [24] Li, S.; Wang, Z.; Liu, J.; Yang, L.; Guo, Y.; Cheng, L.; Lei, M.; Wang, W. Yolk–Shell Sn@C Eggette-Like Nanostructure: Application in Lithium-Ion and Sodium-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 19438-19445. [25] Xia, T.; Zhang, W.; Li, W.; Oyler, N. A.; Liu, G.; Chen, X. Hydrogenated Surface Disorder Enhances Lithium Ion Battery Performance. Nano Energy 2013, 2, 826-835.


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 26

[26] Wang, N.; Yue, J.; Chen, L.; Qian, Y.; Yang, J. Hydrogenated TiO2 Branches Coated Mn3O4 Nanorods as an Advanced Anode Material for Lithium Ion Batteries. ACS Appl. Mater. Interfaces 2015, 7, 10348-10355. [27] Liu, W.; Yuen, W. T.; Stradling, R. A. Preparation of InSb Substrates for Molecular Beam Epitaxy. J. Vac. Sci. Technol. B 1995, 13, 1539-1545. [28] Alfaya, A. A. S.; Gushikem, Y. Highly Dispersed Phosphate Supported in a Binary SilicaTitania Matrix: Preparation and Characterization, Chem. Mater. 1998, 10, 909 -913. [29] Yu, J.; Zhang, L.; Zheng, Z.; Zhao, J. Synthesis and Characterization of Phosphated Mesoporous Titanium Dioxide with High Photocatalytic Activity. Chem. Mater. 2003, 15, 22802286. [30] Wang, Q.; Zhong, L.; Sun, J.; Shen, J. A Facile Layer-by-Layer Adsorption and Reaction Method to the Preparation of Titanium Phosphate Ultrathin Films, Chem. Mater. 2005, 17, 35633569. [31] Komaba, S.; Yabuuchi, N.; Ozeki, T.; Han, Z.-J.; Shimomura, K.; Yui, H.; Katayama, Y.; Miura, T. Comparative Study of Sodium Polyacrylate and Poly-(vinylidene fluoride) as Binders for High Capacity Si-Graphite Composite Negative Electrodes in Li-Ion Batteries, J. Phys. Chem. C 2012, 116, 1380-1389. [32] Yabuuchi, N.; Shimomura, K.; Shimbe, Y.; Ozeki, T.; Son, J.-Y.; Oji, H.; Katayama, Y.; Miura, T.; Komaba, S. Graphite-Silicon-Polyacrylate Negative Electrodes in Ionic Liquid Electrolyte for Safer Rechargeable Li-Ion Batteries. Adv. Energy Mater. 2011, 1, 759-765. [33] Kim, K-T.; Ali, G.; Chung, K. Y.; Yoon, C. S.; Yashiro, H.; Sun, Y-K.; Lu, J.; Amine, K.; Myung, S-T. Anatase Titania Nanorods as an Intercalation Anode Material for Rechargeable Sodium Batteries. Nano Lett. 2014, 14, 416-422.


22

Page 23 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


[34] Lotfabad, E. M.; Kalisvaart, P.; Kohandehghan, A.; Karpuzov, D.; Mitlin, D. Origin of NonSEI Related Coulombic Efficiency Loss in Carbons Tested Against Na and Li. J. Mater. Chem. A 2014, 2, 19685–19695. [35] Hong, K.-S.; Nam, D.-H.; Lim, S.-J.; Sohn, D. R.; Kim, T.-H.; Kwon, H.-S. Electrochemically Synthesized Sb/Sb2O3 Composites as High Capacity Anode Materials Utilizing a Reversible Conversion Reaction for Na-Ion Batteries. ACS Appl. Mater. Interfaces 2015, 7, 17264-17271. [36] Sun, Q.; Ren, Q.-Q.; Li, H.; Fu, Z.-W. High Capacity Sb2O4 Thin Film Electrodes for Rechargeable Sodium Battery. Electrochem. Commun. 2011, 13, 1462-1464. [37] Xu, Y.; Lotfabad, E. M.; Wang, H.; Farbod, B.; Xu, Z.; Kohandehghan, A.; Mitlin, D. Nanocrystalline Anatase TiO2: A New Anode Material for Rechargeable Sodium Ion Batteries. Chem. Commun. 2013, 49, 8973-8975. [38] Liu, S.; Feng, J.; Bian, X.; Liu, J.; Xu, H. The Morphology-Controlled Synthesis of a Nanoporous-Antimony Anode for High-Performance Sodium-Ion Batteries. Energy Environ. Sci. 2016, 9, 1229-1236. [39] Nithya, C.; Gopukumar, S.; RGO/Nano Sb Composite: A High Performance Anode Material for Na+ Ion Batteries and Evidence for the Formation of Nanoribbons from the Nano RGO Sheet During Galvanostatic Cycling. J. Mater. Chem. A 2014, 2, 10516-10525. [40] Zhou, X.; Zhong, Y.; Yang, M.; Hu, M.; Wei, J.; Zhou, Z. Sb Nanoparticles Decorated NRich Carbon Nanosheets as Anode Materials for Sodium Ion Batteries with Superior Rate Capability and Long Cycling Stability. Chem. Commun. 2014, 50, 12888-12891. [41] Nie, A.; Gan, Y.; Cheng, Y.; Tao, X.; Yuan, Y.; Sharifi-Asl, S.; He, K.; Asayesh-Ardakani, H.; Vasiraju, V.; Lu, J.; Mashayek, F.; Klie, R.; Vaddiraju, S.; Schwingenschlogl, U.;


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 26

Shahbazian-Yassar, R. Ultrafast and Highly Reversible Sodium Storage in Zinc-Antimony Intermetallic Nanomaterials. Adv. Funct. Mater. 2016, 26, 543-552. [42] Ko, Y. N.; Kang, Y. C. Electrochemical Properties of Ultrafine Sb Nanocrystals Embedded in Carbon Microspheres for Use as Na-Ion Battery Anode Materials. Chem. Commun. 2014, 50, 12322-12324. [43] Yang, Y.; Yang, X.; Zhang, Y.; Hou, H.; Jing, M.; Zhu, Y.; Fang, L.; Chen, Q.; Ji, X. Cathodically Induced Antimony for Rechargeable Li-Ion and Na-Ion Batteries: the Influences of Hexagonal and Amorphous Phase. J. Power Sources 2015, 282, 358-367. [44] Hou, H.; Jing, M.; Yang, Y.; Zhu, Y.; Fang, L.; Song, W.; Pan, C.; Yang, X.; Ji, X. Sodium/Lithium Storage Behavior of Antimony Hollow Nanospheres for Rechargeable Batteries. ACS Appl. Mater. Interfaces 2014, 6, 16189-16196. [45] Wu, L.; Lu, H.; Xiao, L.; Ai, X.; Yang, H.; Cao, Y. Electrochemical Properties and Morphological Evolution of Pitaya-Like Sb@C Microspheres as High-Performance Anode for Sodium Ion Batteries. J. Mater. Chem. A 2015, 3, 5708-5713. [46] Hou, H.; M. Jing, M.; Zhang, Y.; Chen, J.; Huang, Z.; Ji, X. Cypress Leaf-Like Sb as Anode Material for High-Performance Sodium-Ion Batteries. J. Mater. Chem. A 2015, 3, 17549-17552. [47] Li, W.; Yang, Z.; Li, M.; Jiang, Y.; Wei, X.; Zhong, X.; Gu, L.; Yu, Y. Amorphous Red Phosphorus Embedded in Highly Ordered Mesoporous Carbon with Superior Lithium and Sodium Storage Capacity. Nano Lett. 2016, 16, 1546-1553. [48] Hou, H.; Banks, C. E.; Jing, M.; Zhang, Y.; Ji, X. Carbon Quantum Dots and Their Derivative 3D Porous Carbon Frameworks for Sodium-Ion Batteries with Ultralong Cycle Life. Adv. Mater. 2015, 27, 7861-7866.


24

Page 25 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


[49] Hariharan, S.; Saravanan, K.; Balaya, P. α-MoO3: A High Performance Anode Material for Sodium-Ion Batteries. Electrochem. Commun. 2013, 31, 5-9. [50] Guo, S.; Yu, H.; Liu, P.; Ren, Y.; Zhang, T.; Chen, M.; Ishida M.; Zhou, H. HighPerformance Symmetric Sodium-Ion Batteries Using a New, Bipolar O3-type Material, Na0.8Ni0.4Ti0.6O2. Energy Environ. Sci. 2015, 8, 1237-1244.


25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 26

Table of contents


26

One-Dimensional YolkâShell Sb@TiâOâP ... - ACS Publications

Recommend Documents

One-Dimensional YolkâShell Sb@TiâOâP ... - ACS Publications