LETTER pubs.acs.org/NanoLett
In Situ Transmission Electron Microscopy Observation of Microstructure and Phase Evolution in a SnO2 Nanowire during Lithium Intercalation Chong-Min Wang,*,† Wu Xu,‡ Jun Liu,§ Ji-Guang Zhang,‡ Lax V. Saraf,† Bruce W. Arey,† Daiwon Choi,‡ Zhen-Guo Yang,‡ Jie Xiao,‡ Suntharampillai Thevuthasan,† and Donald R. Baer† †
Environmental Molecular Sciences Laboratory, ‡Energy and Environmental Directorate, and §Fundamental and Computational Science Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States ABSTRACT: Recently we have reported structural transformation features of SnO2 upon initial charging using a configuration that leads to the sequential lithiation of SnO2 nanowire from one end to the other (Huang et al. Science 2010, 330, 1515). A key question to be addressed is the lithiation behavior of the nanowire when it is fully soaked into the electrolyte (Chiang Science 2010, 330, 1485). This Letter documents the structural characteristics of SnO2 upon initial charging based on a battery assembled with a single nanowire anode, which is fully soaked (immersed) into an ionic liquid based electrolyte using in situ transmission electron microscopy. It has been observed that following the initial charging the nanowire retained a wire shape, although highly distorted. The originally straight wire is characterized by a zigzag structure following the phase transformation, indicating that during the phase transformation of SnO2 þ Li T LixSn þ LiyO, the nanowire was subjected to severe deformation, as similarly observed for the case when the SnO2 was charged sequentially from one end to the other. Transmission electron microscopy imaging revealed that the LixSn phase possesses a spherical morphology and is embedded into the amorphous LiyO matrix, indicating a simultaneous partitioning and coarsening of LixSn through Sn and Li diffusion in the amorphous matrix accompanied the phase transformation. The presently observed composite configuration gives detailed information on the structural change and how this change takes place on nanometer scale. KEYWORDS: Li-ion battery, in situ TEM, microstructure, nanobattery, SnO2 nanowire
O
ne of the greatest challenges facing Li-ion battery development16 is solving the gradual capacity fading that accompanies each cyclic charge and discharge of a battery. Capacity fading is generally perceived to be a direct consequence of the irreversible microstructural evolutions of the active materials in a battery.25,7 With the SnO2 anode as an example, it is known that upon initial charging to ca. 0.9 V vs Liþ/Li, the SnO2 is transformed to Sn and Li2O. Subsequent charging and discharging of the battery corresponds to the reversible phase transformation of Sn þ xLiþ þ xe T LixSn (0 e x e 4.4).8,9 However, how the microstructure evolves upon such an irreversible phase transformation following the initial charging (the spatial relationship between the Sn and the Li2O) is not known. Advanced diagnostic tools, such as electron microscopy and other surface- and bulk-sensitive tools (often in ex situ mode), are indispensible tools for probing into the structural evolution of active materials in a Li-ion battery as a function of charging and/ or discharging.1012 However, because the structure is mostly stable under operating conditions only, characterizing this structure using an ex situ capability is a challenge and not always reliable.1,9,1319 In situ methods based on spectroscopic methods,2,3,13,20,21 scanning probe microscopy (SPM),2,22,23 scanning electron microscopy (SEM) imaging,24,25 and X-ray diffraction (XRD)8 have provided useful information regarding the structural evolution of the electrode materials during the operation of a battery. Some of these methods normally have r 2011 American Chemical Society
limited spatial resolution. In situ transmission electron microscopy (TEM) imaging and associated spectroscopic techniques are generally regarded as ideal tools for probing the structural evolution of materials during their operation21,24,2631 if appropriate operation conditions can be established. In-situ battery operation in the high vacuum of a TEM has been pursued following two ideas. For a liquid electrolyte based battery, the whole system may be sealed within a membrane to prevent the evaporation of the liquid electrolyte, and the membrane must be thin enough to allow the transmission of the electrons. This strategy holds significant challenges for cell fabrication used for in situ TEM observation.27 A second approach investigated a thin slice of solid-state battery created using focused ion beam (FIB) slicing of a thin-film battery.32,33 Recently, Wang et al.28 and Huang et al.34 have described an alternate in situ TEM methods using ionic liquid-based electrolyte and a single nanowire electrode. Because an ionic liquid-based electrolyte is normally vacuum compatible, exhibiting a very low vapor pressure, a model battery construction is simplified.3537 A Li-ion battery using an ionic liquid-based electrolyte can be directly loaded into a TEM without sealing the whole system within a membrane; Received: October 8, 2010 Revised: April 1, 2011 Published: April 08, 2011 1874
dx.doi.org/10.1021/nl200272n | Nano Lett. 2011, 11, 1874–1880
Nano Letters
Figure 1. TEM, HRTEM, electron diffraction, and field emission SEM analysis of the SnO2 nanowire: (a) bright-field image, (b) dark-field image, (c) HRTEM image with the nanowire growth direction marked. The inset on top is the selected area electron diffraction pattern, which clearly indicates the growth direction of the nanowire is Æ201æ. The inset at the bottom is a field emission SEM image showing the general morphology of the SnO2 nanowire.
therefore, unprecedented high spatial resolution TEM imaging can be obtained during the operation of the battery. In a model experiment using SnO2 nanowire as the anode, ionic liquid-based electrolyte as the electrolyte, and LiCoO2 as the cathode, Huang et al34 have observed that upon initial charging the SnO2 went through an electrochemical induced solid state amorphization process,38 which is accompanied by elongation and thickening in diameter of the nanowire. In that experiment, one end of the SnO2 nanowire is inserted into the electrolyte and, under a constant biasing against the LiCoO2 cathode, the reaction propagates sequentially from one end to the other of the nanowire. This configuration is contrasted to the real situation of a battery for which the electrode is normally fully soaked into the electrolyte. Therefore, it is important to explore the structure and phase evolution of the SnO2 under the configuration of fully soaked into the electrolyte.39 As SnO2 represents a category of metal oxide based anode material for the Li-ion battery, which is commonly featured by the irreversible conversion or displacement upon initial charging, the structure and phase, especially the spatial correlation between newly formed phases, are of great importance for understanding the electrochemical behavior of this category of metal oxide for Liion battery. In this Letter, we report the structure and phase evolution of the SnO2 upon initial charging using a configuration of soaking the SnO2 nanowire into the ionic liquid based electrolyte. The morphology and the crystallographic features of the synthesized SnO2 nanowires are shown in Figure 1. The SnO2 nanowire anode, which has the advantage of electron transparency and allows in situ observation of chemical and structural change under the TEM during battery operation, was synthesized by a chemical vapor deposition process using active carbon and SnO2 nanoparticles as precursors.40,41 The diameter of the
LETTER
Figure 2. Schematic drawing, field emission SEM, and optical images showing the conceptual design of the miniature battery using an ionic liquid-based electrolyte, LiCoO2, as the cathode and SnO2 nanowire as the anode: (a) overall assembly of the miniature battery; (b) field emission SEM image showing the Pt welding at the contact region between the W wire and the SnO2 nanowire; (c) schematic drawing showing the biasing holder; and (d) reflective optical image showing the SnO2 nanowire anode dipped into the ionic liquid electrolyte, which is placed on LiCoO2 cathode.
SnO2 wire ranged from several nanometers to ∼1 μm, and the length of the wire ranged from several hundred nanometers to several hundred micrometers. Bright-field and dark-field TEM imaging, electron diffraction, and high-resolution TEM (HRTEM) imaging indicated that the nanowires grew along the Æ201æ direction. The crystalline structural nature of the SnO2 nanowire also was confirmed by XRD. The overall conceptual integration of the miniature battery is schematically illustrated in Figure 2, which is described in detail in a previous publication, and here is a brief summary.28 The LiCoO2 cathode sheet was made via a conventional electrode preparation method, i.e., casting a slurry of mixtures of LiCoO2 particles, conductive carbon, and poly(vinylidene fluoride) binder in N-methylpyrrolinium onto aluminum foil. The electrolyte was prepared by dissolving an air-stable salt, LiTFSI, in a hydrophobic ionic liquid, P14TFSI. The salt concentration of the electrolyte was 10 wt % LiTFSI in P14TFSI. A volatile test indicated that this ionic liquid-based electrolyte had no obvious loss in the column of the TEM with a typical vacuum of 105 Pa for 1 week, thereby allowing for systematic cyclic charging and discharging of the battery in the TEM. The overall assembly of the microbattery is shown in Figure 2a. A single SnO2 nanowire was picked up under an optical microscope and attached to the tip of a W wire. The diameter of the W wire was 250 μm, which was honed to a sharp tip using an electrochemical etching process typically used for making tips for scanning probe microscopes. To provide a good electrical connection between the SnO2 nanowire and the W wire, the contact region between the SnO2 nanowire and the W wire was welded by depositing Pt at the joint using an FIB in a dual-beam FIB/SEM (Helios, FEI) as shown in the SEM image in Figure 2b. The SnO2 nanowire anode and the LiCoO2 cathode 1875
dx.doi.org/10.1021/nl200272n |Nano Lett. 2011, 11, 1874–1880
Nano Letters
Figure 3. (a) Charging curve (potential as a function of time) of the miniature battery. (b) TEM bright-field image shows the SnO2 nanowire anode before the charging. The inset at the top-left corner of (b) is a lowmagnification image revealing the overall straight morphology of the SnO2 nanowire. The inset at the lower-right corner of (b) shows the electron diffraction pattern of the nanowire, indicating the single crystal structure of the SnO2 nanowire. (c) TEM bright-field image reveals the microstructure of the nanowire anode following the initial charging of ∼14 h. The inset at the top-left corner of (c) is a low-magnification image revealing that, following the initial charging, the originally straight SnO2 nanowire evolves to a zigzag morphology. (d) TEM bright-field image showing the structural features of another region on the nanowire following the charging of ∼14 h. Detailed structure and composition analyses are presented in Figures 4 and 5.
assembly were integrated on a specially designed module, which was inserted into the biasing TEM holder as shown in Figure 2c. A small drop of the ionic liquid-based electrolyte was placed on the top of the LiCoO2 cathode. The SnO2 nanowire anode was dipped into the electrolyte (Figure 2a and Figure 2d). The integrated miniature prototype Li-ion battery module was inserted into the biasing TEM holder, which was designed and fabricated by Hummingbird Scientific (Lacey, Washington, USA) for the in situ TEM testing of the Li-ion battery. The biasing TEM holder was connected to an electrochemical workstation (model CHI 660C, CH Instruments, Texas, USA) for the charge operation of the battery. Figure.3a shows a representative charging curve of the miniature battery assembled using the single nanowire illustrated in Figure 3b. The battery was galvanostatically charged with a total current of 0.1 μA at the cell potential ranging from 2.6 to 4.0 V. The key question to be answered is how the microstructure and phase evolve in the SnO2 nanowire anode during the charging process. For the battery configuration assembled with a single nanowire as illustrated in Figure 2, the most interested region on the nanowire is the section that is fully immersed into the electrolyte and overlapped with the LiCoO2 cathode. By use of TEM imaging, electron diffraction, electron energy loss spectroscopy (EELS), and energy dispersive X-ray spectroscopy (EDS), the microstructural features of this region were monitored following the charging. This section of the SnO2 nanowire anode
LETTER
Figure 4. TEM imaging, nanobeam and selected area electron diffraction, and HRTEM imaging reveal the structural features of the nanowire following the initial charging shown in Figure 3. (a) A bright-field TEM image showing the dark-contrasted particles dispersed in a relatively light-contrasted matrix. (b) HRTEM image reveals the dark-contrasted particle is crystalline. (c) Nanobeam electron diffraction pattern shows the light-contrasted matrix is amorphous. (d) Selected area electron diffraction pattern reveals that the dark-contrasted particles can be indexed as Li22Sn5 with the space group F23.
shows substantial structural and phase evolutions as illustrated by the comparison of the TEM images shown in panels b, c, and d of Figure 3. Two significant microstructural changes can be seen— one related to the overall morphological change of the nanowire and the other to the phase change. Prior to the initial charge, the SnO2 nanowire is a single crystal and possesses an overall straight morphology as illustrated by the low-magnification TEM image shown as an inset in Figure 3b. Following the initial charging as indicated in Figure 3a, the nanowire maintains a wire morphology, but it is no longer a straight wire. Instead, the nanowire features a zigzag morphology as illustrated by the low-magnification TEM image shown in the inset of Figure 3c. Therefore, at a relatively large scale, the straight nanowire was subjected to a dynamical structural evolution during the charging, which is characterized by the curving of the initially straight nanowire. Similar structural features have been observed when the SnO2 nanowire was lithiated sequentially from one end to the other.34 Therefore, it can be generally concluded that regardless of the nanowire being either fully soaked or with a configuration leading to lithiation sequentially from one end to the other, the nanowire can accommodate the mechanical deformation related to lithiation induced volume expansion as compared with its bulk counterpart. It remains to be established if there exists a critical diameter above which the nanowire may behave like a bulk material. We have noticed for one occasion that a nanowire of a diameter of 1 μm shows local cracking following the initial lithiation. More systematic work is needed to explore this size effect. The curving of the nanowire is a direct consequence of the strain relaxation associated with the phase transformation upon lithiation: SnO2 þ Li T LixSn þ LiyO. Prior to the initial charging and at a finer scale, the whole SnO2 nanowire is a single crystal as demonstrated by the electron diffraction pattern of the inset in 1876
dx.doi.org/10.1021/nl200272n |Nano Lett. 2011, 11, 1874–1880
Nano Letters
LETTER
Figure 5. TEM imaging, EELS, and EDS chemical composition analyses of the nanowire following the initial charging of ∼14 h as shown in Figure 3, conforming the dark-contrasted particles are LixSn and the light-contrasted matrix is LiyO. The small Sn peak on the EDS from the LiyO region is believed to be contributed by the electron scattering to hit the neighboring LixSn particle.
Figure 3b. Following the initial charging of ∼14 h (Figure.3a), the nanowire is characterized by the dark-contrasted, spherically shaped particles that are dispersed into a slightly light-contrasted matrix as shown by panels c and d of Figure 3. Due to the deformation of the nanowire following the reaction, the images shown in panels b and c of Figure 3(b) and (c) do not correspond to the exact same region. As marked in panels c and d of Figure 3, the dark-contrasted spherically shaped particles are crystalline LixSn, while the light-contrasted matrix structure is an amorphous LiyO as evidenced by the electron diffraction, HRTEM imaging, and chemical composition presented in Figures 46. Figure 4b is a HRTEM lattice image of the edge of the particle marked in Figure 4a, revealing the crystalline structural nature of this particle. Figure 4c shows the nanobeam electron diffraction pattern from the light-contrasted region as marked in Figure 4a, demonstrating that the light-contrasted region is amorphous. Detailed analysis of the selected area electron diffraction pattern shown in Figure.4d indicates that the crystalline phase is Li22Sn5 with a space group of F23 of cubic structure.42 EELS and EDS chemical composition analysis as illustrated in Figures 5 and 6 confirm that the dark-contrasted, spherically shaped particles are LixSn, while the light-contrasted matrix is LiyO. As illustrated in Figure 6, overlapping of the O K-edge and Sn M-edge on the EELS spectra makes it hard to accurately extract the concentration of possible O in the LixSn and Sn in the LiyO phases. EDS analysis indicates no measurable O in the LixSn particle and that the LiyO matrix is depleted from Sn. (It should be noted that as shown at the bottom panel of Figure 5, on the EDS from the LiyO region there exists a small Sn peak, which is believed to be contributed by the electron beam scattering to hit the neighboring LixSn particle.) It should be noticed that the Li K-edge observed on both LixSn and LiyO is also contributed in principle by the Li in the electrolyte. However, as illustrated in Figure 6, EELS collected
Figure 6. (a) TEM image showing a drop of ionic liquid based electrolyte on the SnO2 nanowire and the corresponding EELS spectra from the electrolyte. (b) Peak related to Li K-edge is not visible for the electrolyte. (c) EELS spectra of SnO2 showing the overlapping of O K-edge and Sn M-edge.
on the electrolyte shows no significant peak related to Li K-edge, demonstrating that the peak related to Li K-edge shown in Figure 5 is dominated by the Li in LixSn and LiyO. EELS should be a powerful tool to determine the Li concentration within the specific phase. However, because the peak of the Li K-edge sits just on the plasmon loss peak, this complicates the reliable subtraction of background for quantitative analysis of Li concentration. Therefore, no attempt was made for quantifying the 1877
dx.doi.org/10.1021/nl200272n |Nano Lett. 2011, 11, 1874–1880
Nano Letters
LETTER
Figure 7. Schematic drawing showing the structure and phase evolution of the SnO2 upon initial charging, featuring the initial solid state amorphization, followed by the nucleation and growth of LixSn from the amorphous (Li, Sn, O) phase, subsequent coarsening of the LixSn, and depletion of Sn from the (Li, Sn, O) amorphous phase, leading to the final amorphous phase as LiyO.
values of x and y for LixSn and LiyO, respectively. Graetz et al.43 have attempted to use EELS to quantify the concentration of Li inserted into their electrode materials and they similarly noticed that the quantification is not reliable due to the difficulty on the background subtraction beneath the Li K-edge. More systematic work is needed in order to reliably quantify the Li concentration using EELS. In general, it is known that an electron beam can modify the microstructure of the materials.44 For the case of the present work, to minimize the effect of the electron beam on the sample, the beam was “blanked” during the charging process. During the imaging, care was taken to keep a low electron dose by spreading the electron beam spread over large areas. Therefore, electron beam modification of the general microstructure presented in the paper is at minimum. It has been very well established that the first charging of SnO2 anode material to ca. 0.9 V vs Liþ/Li is known to lead to the formation of metallic tin and lithium oxide, and the subsequent charging and discharging are related to the reversible phase transformation of Sn þ xLiþ þ xe T LixSn (0 e x e 4.4).8 However, no detailed structural information has ever been reported regarding the spatial distribution and correlation between the newly formed LixSn and LiyO phases. The present TEM imaging, electron diffraction, EELS, and EDS compositional analyses provide key insights on the structural evolution and subsequent spatial correlation of newly formed phases LixSn and LiyO following the initial charging of the SnO2 nanowire. Fundamentally, the crystalline LixSn possesses spherical morphology and is dispersed in the amorphous structured LiyO matrix, essentially forming a unique composite structure. Due to the binding effect of the LiyO, the initial morphology of SnO2 is still preserved following the phase transformation. Previously, based on electrochemical properties measurement and in situ X-ray diffraction techniques, it has been inferred that the tin is likely dispersed into a lithium oxide matrix, and it is generally believed that such a composite structure accounts for the integrity of the tin particles as an electrode.8,45 The presently observed microstructural evolution provides direct evidence for these speculations based on indirect experimental results regarding the spatial correlation of LixSn and LiyO in the literature. It has also been observed that LixSn particles have a wider size distribution (Figure 3c,d and Figure 4a), indicating that the simultaneous partitioning and coarsening of LixSn particles through the diffusion of Sn and Li in the amorphous LiyO matrix accompanies the phase transformation. It is known that for the metal oxide based anode material, such as SnO2, the initial charging is featured by solid state amorphization.34,38 Due the fully soaked configuration of the SnO2 in the electrolyte, we cannot directly capture the initial solid state amorphization
process. On the basis of the present observation as well as that which has been reported previously,34 we summarize the structural evolution of SnO2 upon initial charging by the schematic drawing shown in Figure 7, which is featured by initial solid state amorphization, nucleation, and growth of LixSn from the amorphous (Li, Sn, O) matrix, subsequent coarsening of the LixSn, and depletion of Sn from the initial (Li, Sn, O) amorphous phase, leading to the final amorphous phase as LiyO. One of the sensible questions that may be raised is how does the microstructure evolve during the discharging and subsequent cyclic charging and discharging of the battery following the initial charging. We have realized that the single nanowire battery was basically damaged by the severe deformation of the nanowire following the initial charging (such as curving and spiraling). Therefore, no discharge experiment has been carried out. With improved experimental design in the future, we would expect to catch the dynamic structural evolution during the charging and discharging process. This composite structure of LixSn spherical particles dispersed in the LiyO has several advantages. First, the LiyO behaves as a glue to maintain the structural integrity of the whole anode system. Second, LiyO keeps the LixSn particles dispersed and prevents a large-scale conglomeration of the LixSn particles in the subsequent cycling, therefore enabling a fast charging rate of the battery system. Third, as LiyO is an insulator, the electrical conductivity of the whole system will be critically determined by the connectivity of the LixSn particles in the LiyO matrix, which depends on the morphology and size of the particle, because the volume ratio of LixSn/LiyO is fixed with respect to the reaction SnO2 þ Li T LixSn þ LiyO. Work is needed to identify the controlling factors that critically affect the nucleation and growth mechanism of the LixSn in the matrix of LiyO. Typically, the observed direct spatial correlation of the LixSn particle and the amorphous LiyO implies that coarsening of the LixSn can be minimized by using nanoscale SnO2 starting particles. Furthermore, conductive additives may also be added to prevent the coarsening of the nanosized LixSn particles. Using a model system of a SnO2 single-nanowire-based battery, direct microstructural features on the structure and phase evolution of SnO2 upon lithiation have been captured, characterized by a unique composite structure with LixSn spherical particles dispersed in the amorphous-structured, matrix-like LiyO. The basic design concept for probing into the microstructural evolution of anode (or cathode) material using a single nanowire anode (or cathode) and an ionic liquid-based electrolyte represents a very clean approach for identifying the key microstructural features of a battery system, which excludes 1878
dx.doi.org/10.1021/nl200272n |Nano Lett. 2011, 11, 1874–1880
Nano Letters complication of the microstructure by the addition of binders and conductive materials in a coin cell for postmortem analysis. It should be realized that the present work represents preliminary results on the initial lithiation of SnO2. It has been demonstrated that in combination with nanomanipulations in a TEM,34 the present model work can be applied in parallel to explore the dynamic microstructural and phase evolution of anode and cathode materials system upon lithiation and delithiation, and these results will be reported in detail in future work. Furthermore, controlled lithiation and delithiation in combination with direct quantitative microstructural analysis will enable correlation of microstructural evolution features with mass and charge transport kinetics and mechanisms in a battery system.
’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected].
’ ACKNOWLEDGMENT The authors thank Dr. Jianyu Huang of Sandia National Laboratory for beneficial discussions, Michael C. Perkins of Pacific Northwest National Laboratory (PNNL) for the graphic work of Figure 2, Drs. Yuliang Cao and Libor Kovarik for critical discussions and reading the manuscript, and Norman Salmon of Hummingbird Scientific for designing and manufacturing of the biasing holder. This work was supported in part by the Laboratory Directed Research and Development (LDRD) program of Pacific Northwest National Laboratory, and Offices of Basic Energy Sciences and Biological and Environmental Research, Office of Science of U.S. Department of Energy (DOE). Jun Liu is grateful for the support from the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award KC020105FWP12152. The work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at PNNL. PNNL is operated by Battelle for the DOE under Contract DE-AC05-76RLO1830. ’ REFERENCES (1) Tarascon, J. M.; Armand, M. Nature 2001, 414, 359. (2) Kong, F.; Kostecki, R.; Nadeau, G.; Song, X.; Zaghib, K.; Kinoshita, K.; McLarnon, F. J. Power Sources 2001, 9798, 58. (3) Bryngelsson, H.; Stjerndahl, M.; Gustafsson, T.; Edstrom, K. J. Power Sources 2007, 174, 970. (4) Ota, H.; Akai, T.; Namita, H.; Yamaguchi, S.; Nomura, M. J. Power Sources 2003, 119121, 567. (5) Retoux, R.; Brousse, T.; Schleich, D. M. J. Electrochem. Soc. 1999, 146, 2472. (6) Chung, S. Y.; Bloking, J. T.; Chiang, Y. M. Nat. Mater. 2002, 1, 123. (7) Li, H.; Huang, X.; Chen, L. Q. Electrochem. Solid-State Lett. 1998, 1, 241. (8) Courtney, I. A.; Dahn, J. R. J. Electrochem. Soc. 1997, 144, 2045. (9) Idota, Y.; Kubota, T.; Matsufuji, A.; Maekawa, Y.; Miyasaka, T. Science 1997, 276, 1395. (10) Shao-Horn, Y.; Croguennec, L.; Delmas, C.; Nelson, E. C.; O’Keefe, M. A. Nat. Mater. 2003, 2, 464.
LETTER
(11) Thackeray, M. M.; Shao-Horn, Y.; Kahaian, A. J.; Kepler, K. D.; Skinner, E.; Vaughey, J. T.; Hackney, S. A. Electrochem. Solid-State Lett. 1998, 1, 7. (12) Choi, S.; Manthiram, A. J. Electrochem. Soc. 2002, 149, A1157. (13) Dedryvere, R.; Martinez, H.; Leroy, S.; Lemordant, D.; Bonhomme, F.; Biensan, P.; Gonbeau, D. J. Power Sources 2007, 174, 462. (14) Nishimura, S. I.; Kobayashi, G.; Ohoyama, K.; Kanno, R.; Yashima, M.; Yamada, A. Nat. Mater. 2008, 7, 707. (15) Gibot, P.; Casas-Cabanas, M.; Laffont, L.; Levasseur, S.; Carlach, P.; Hamelet, S.; Tarascon, J. M.; Masquelier, C. Nat. Mater. 2008, 7, 741. (16) Delmas, C.; Maccario, M.; Croguennec, L.; Cras, F. L.; Weill, F. Nat. Mater. 2008, 7, 665. (17) Mauchamp, V.; Moreau, P.; Moncondut, L.; Doublet, M. L.; Boucher, F.; Ouvrard, G. J. Phys. Chem. C 2007, 111, 3996. (18) M€ollera, K. C.; Santner, H. J.; Kern, W.; Yamaguchi, S.; Besenhard, J. O.; Winter, M. J. Power Sources 2003, 119121, 561. (19) Mai, L. Q.; Dong, Y. J.; Xu, L.; Han, C. H. Nano Lett. 2010, 10, 4273. (20) Laffont, L.; Delacourt, C.; Gibot, P.; Wu, M. Y.; Kooyman, P.; Masquelier, C.; Marie Tarascon, J. Chem. Mater. 2006, 18, 5520. (21) Chen, G. Y.; Song, X. Y.; Richardson, T. J. Electrochem. SolidState Lett. 2006, 9, A295. (22) Lucas, I. T.; Pollak, E.; Kostecki, R. Electrochem. Commun. 2009, 11, 2157. (23) Balke, N.; Jesse, S.; Morozovska, A. N.; Eliseev, E.; Chung, D. W.; Kim, Y.; Adamczyk, L.; García, R. E.; Dudney, N.; Kalinin, S. V. Nat. Nanotechnol. 2010, 749–754. (24) Yang, Y.; Xie, C.; Ruffo, R.; Peng, H. L.; Kim, D. K.; Cui, Y. Nano Lett. 2009, 9, 4109. (25) Raimann, P. R.; Hochgatterer, N. S.; Korepp, C.; M€oller, K. C.; Winter, M.; Schr€ottner, H.; Hofer, F.; Besenhard, J. O. Ionics 2006, 12, 253. (26) Eswaramoorthy, S. K.; Howe, J. M.; Muralidharan, G. Science 2007, 318, 1437. (27) Williamson, M. J.; Tromp, R. M.; Vereecken, P. M.; Hull, R.; Ross, F. M. Nat. Mater. 2003, 2, 532. (28) Wang, C. M.; Xu, W.; J., L.; Choi, D. W.; Arey, B.; Saraf, L. V.; Zhang, J. G.; Yang, Z. G.; Thevuthasan, S.; Baer, D. R.; Salmon, N. J. Mater. Res. 2010, 25, 1541. (29) Frank, S.; Poncharal, P.; Wang, Z. L.; de Heer, W. A. Science 1998, 280, 1744. (30) Xiang, J.; Lu, W.; Hu, Y. J.; Wu, Y.; Yan, H.; Lieber, C. M. Nature 2006, 441, 489. (31) Cui, Y.; Lieber, C. M. Science 2001, 291, 851. (32) Brazier, A.; Dupont, L.; Dantras-Laffront, L.; Kuwata, N.; Kawamura, J.; Tarascon, J. M. Chem. Mater. 2008, 20, 2352. (33) Yamamoto, K.; Iriyama, Y.; Asaka, T.; Hirayama, T.; Fujita, H.; Fisher, C. A. J.; Nonaka, K.; Sugita, Y.; Ogumi, Z. Angew. Chem., Int. Ed. 2010, 49, 4414. (34) Huang, J. Y.; Zhong, L.; Wang, C. M.; Sullivan, J. P.; Xu, W.; Zhang, L. Q.; Mao, S. X.; Hudak, N.; Liu, X. H.; Subramanian; Fan, H. Y.; Qi, L.; Kushima, A.; Li, J. Science 2010, 330, 1515. (35) Lux, S. F.; Schmuck, M.; Rupp, B.; Kern, W.; Appetecchi, G. B.; Passerini, S.; Winter, M.; Balducci, A. ECS Trans. 2009, 16, 45. (36) Lewandowski, A.; Swiderska-Mocek, A. J. Power Sources 2007, 171, 938. (37) Howlett, P. C.; MacFarlane, D. R.; Hollenkamp, A. F. Electrochem. Solid-State Lett. 2004, 7, A97. (38) Limthongkul, P.; Jang, Y.; Nancy, J. D.; Chiang, Y., M Acta Mater. 2003, 51, 1103. (39) Chiang, Y. M. Science 2010, 330, 1485. (40) Wang, J. X.; Liu, D. F.; Yan, X. Q.; Yuan, H. J.; Ci, L. J.; Zhou, Z. P.; Gao, Y.; Song, L.; Liu, L. F.; Zhou, W. Y.; Wang, G.; Xie, S. S. Solid State Commun. 2004, 130, 89. (41) Pan, Z. W.; Dai, Z. R.; Wang, Z. L. Science 2001, 291, 1947. (42) Dahn, J. R.; Courtney, I. A.; Mao, O. Solid State Ionics 1998, 111, 289. 1879
dx.doi.org/10.1021/nl200272n |Nano Lett. 2011, 11, 1874–1880
Nano Letters
LETTER
(43) Graetz, J.; Ahn, C. C.; Yazami, R.; Fultz, B. J. Phys. Chem. B 2003, 107, 2887. (44) Wang, C. M.; Baer, D. R.; Amonette, J. E.; Engelhard, M. H.; Antony, J. J.; Qiang, Y. Ultramicroscopy 2007, 108, 43. (45) Nazar, L. F.; Crosnier, O. Anodes and Composite Anodes: An Overview; Kluwer Academic Publishers: Boston and New York, 2004.
1880
dx.doi.org/10.1021/nl200272n |Nano Lett. 2011, 11, 1874–1880
