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Hierarchical Li4Ti5O12/TiO2 composite tubes with regular structural imperfection for lithium ion storage.

Jiang YM, Wang KX, Zhang HJ, Wang JF, Chen JS - Sci Rep (2013)

Bottom Line: Hierarchical Li4Ti5O12/TiO2 tubes composed of ultrathin nanoflakes have been successfully fabricated via the calcination of the hydrothermal product of a porous amorphous TiO2 precursor and lithium hydroxide monohydrate.The regular structural imperfection existed in the nanoflakes also benefit to lithium ion storage property of these tubes.The hierarchical Li4Ti5O12/TiO2 tubes are a promising anode material for lithium-ion batteries with high power and energy densities.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.

ABSTRACT
Hierarchical Li4Ti5O12/TiO2 tubes composed of ultrathin nanoflakes have been successfully fabricated via the calcination of the hydrothermal product of a porous amorphous TiO2 precursor and lithium hydroxide monohydrate. The hierarchical tubes are characterized by powder X-ray diffraction, nitrogen adsorption/desorption, scanning electron microscopy and transmission electron microscopy techniques. These nanoflakes exhibit a quite complex submicroscopic structure with regular structural imperfection, including a huge number of grain boundaries and dislocations. The lithium ion storage property of these tubes is evaluated by galvanostatic discharge/charge experiment. The product shows initial discharge capacities of 420, 225, and 160 mAh g(-1) at 0.01, 0.1, and 1.0 A g(-1), respectively. After 100 cycles, the discharge capacity is 139 mAh g(-1) at 1.0 A g(-1) with a capacity retention of 87%, demonstrating good high-rate performance and good cycleability. The high electrochemical performance is attributed to unique structure and morphology of the tubes. The regular structural imperfection existed in the nanoflakes also benefit to lithium ion storage property of these tubes. The hierarchical Li4Ti5O12/TiO2 tubes are a promising anode material for lithium-ion batteries with high power and energy densities.

No MeSH data available.


Related in: MedlinePlus

Schematic drawing and electron microscopy images of the nanoflake.(a) Schematic representation of a structural model of the nanoflake, showing a regular lamellar structure with defects. (b, c) High resolution TEM (HRTEM) images of the nanoflake in region I. Regular structural imperfection with an average distance of approximately 1.7 nm is clearly observed in the TEM image (b). In the SAED pattern inset in b, the electron diffraction along the [011] zone axis (perpendicular to the nanoflake surface) is indexed to the cubic structure of spinel Li4Ti5O12, each stacked layer are offset and stepping upwards layer by layer like a staircase (c). (d, e, f) HRTEM images of the nanoflake in region II. The layers stacked in the nanoflakes form a dihedral angel {111} vs. {111} of approximately 70.5°, consistent with the cubic structure of Li4Ti5O12. Grain boundaries and dislocations present in the nanoflakes (f). (g) HRTEM image of the nanoflake in region III, confirming the co-existence of the spinel Li4Ti5O12 and anatase TiO2.
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f2: Schematic drawing and electron microscopy images of the nanoflake.(a) Schematic representation of a structural model of the nanoflake, showing a regular lamellar structure with defects. (b, c) High resolution TEM (HRTEM) images of the nanoflake in region I. Regular structural imperfection with an average distance of approximately 1.7 nm is clearly observed in the TEM image (b). In the SAED pattern inset in b, the electron diffraction along the [011] zone axis (perpendicular to the nanoflake surface) is indexed to the cubic structure of spinel Li4Ti5O12, each stacked layer are offset and stepping upwards layer by layer like a staircase (c). (d, e, f) HRTEM images of the nanoflake in region II. The layers stacked in the nanoflakes form a dihedral angel {111} vs. {111} of approximately 70.5°, consistent with the cubic structure of Li4Ti5O12. Grain boundaries and dislocations present in the nanoflakes (f). (g) HRTEM image of the nanoflake in region III, confirming the co-existence of the spinel Li4Ti5O12 and anatase TiO2.

Mentions: Figure 2 shows further structural feature of the hierarchical Li4Ti5O12/TiO2 tubes. A schematic illustration of the individual nanoflake is drawn to show the regions revealed by the HRTEM observation (Figure 2a). The HRTEM image of the nanoflake taken in region I clearly exhibits a periodic arrangement of fringes with an average distance of approximately 1.7 nm, obviously larger than the lattice fringe spacings of Li4Ti5O12 and TiO2 (Figure 2b). The lattice-fringe-like periodic pattern is believed to be derived from defects, demonstrating the regular structural imperfection of these nanoflakes. However, the corresponding selected area electron diffraction (SAED) (inset in Figure 2b) along the [011] zone axis (perpendicular to the nanoflake surface) exhibits a series of spot pattern, characteristic for a single-crystal-like structure. All of the diffraction spots can be well indexed to the spinel Li4Ti5O12 with a cubic structure in which the direction [hkl] is perpendicular to the (hkl) plane. Therefore, it can be concluded that the Li4Ti5O12 nanoflakes are bound by (011) facets on both the top and bottom surfaces. The HRTEM images (Figure 2c, d) of the nanoflake in region I and II are taken along the direction that almost parallels with the nanoflake plane. As shown in Figure 2c, the lattice fringes with a spacing of 0.50 nm attributing to the (111) plane of spinel Li4Ti5O12 with a lattice fluctuation are clearly observed. A careful examination of the HRTEM image indicates that structural imperfection is derived from the interlacing of two or three closely packed parallel (111) planes. This layer-by-layer-like stacking can be clearly observed in the TEM images viewing along or perpendicular to the surface of the nanoflakes (Figure 2d, e). The interlayer spacing of the lattice-fringe-like structural imperfection is approximately 1.7 nm, consistent with that observed in Figure 2b. For a cubic structure, the dihedral angle between the (111) planes is 70.5°. Distinct lattice fringes with a distance of approximately 0.48 nm are observed, corresponding to the (111) planes of spinel Li4Ti5O12 (Figure 2e). The angle between these lattice fringes is approximately 70.5°, consistent with the cubic structure of Li4Ti5O12. It is interesting that plenty of grain boundaries exist among the crystalline domains in the nanoflakes (Figure 2f). These attractive grain boundaries are expected to provide extra diffusion path and storage sites for lithium ions. Figure 2g shows the HRTEM image taken in region III, the root section of the nanoflake. The lattice fringe spacings of 0.49 and 0.36 nm observed are ascribed to the (111) plane of spinel Li4Ti5O12 and (101) plane of anatase TiO2, respectively, confirming the co-existence of the spinel Li4Ti5O12 and anatase TiO2. In addition, a great deal of grain boundaries among the spinel Li4Ti5O12 and anatase TiO2 are also observed in the region. The HRTEM observation is in agreement with that of the XRD analysis. The presence Li4Ti5O12 and TiO2 dual phase significantly increases the grain boundary density.


Hierarchical Li4Ti5O12/TiO2 composite tubes with regular structural imperfection for lithium ion storage.

Jiang YM, Wang KX, Zhang HJ, Wang JF, Chen JS - Sci Rep (2013)

Schematic drawing and electron microscopy images of the nanoflake.(a) Schematic representation of a structural model of the nanoflake, showing a regular lamellar structure with defects. (b, c) High resolution TEM (HRTEM) images of the nanoflake in region I. Regular structural imperfection with an average distance of approximately 1.7 nm is clearly observed in the TEM image (b). In the SAED pattern inset in b, the electron diffraction along the [011] zone axis (perpendicular to the nanoflake surface) is indexed to the cubic structure of spinel Li4Ti5O12, each stacked layer are offset and stepping upwards layer by layer like a staircase (c). (d, e, f) HRTEM images of the nanoflake in region II. The layers stacked in the nanoflakes form a dihedral angel {111} vs. {111} of approximately 70.5°, consistent with the cubic structure of Li4Ti5O12. Grain boundaries and dislocations present in the nanoflakes (f). (g) HRTEM image of the nanoflake in region III, confirming the co-existence of the spinel Li4Ti5O12 and anatase TiO2.
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f2: Schematic drawing and electron microscopy images of the nanoflake.(a) Schematic representation of a structural model of the nanoflake, showing a regular lamellar structure with defects. (b, c) High resolution TEM (HRTEM) images of the nanoflake in region I. Regular structural imperfection with an average distance of approximately 1.7 nm is clearly observed in the TEM image (b). In the SAED pattern inset in b, the electron diffraction along the [011] zone axis (perpendicular to the nanoflake surface) is indexed to the cubic structure of spinel Li4Ti5O12, each stacked layer are offset and stepping upwards layer by layer like a staircase (c). (d, e, f) HRTEM images of the nanoflake in region II. The layers stacked in the nanoflakes form a dihedral angel {111} vs. {111} of approximately 70.5°, consistent with the cubic structure of Li4Ti5O12. Grain boundaries and dislocations present in the nanoflakes (f). (g) HRTEM image of the nanoflake in region III, confirming the co-existence of the spinel Li4Ti5O12 and anatase TiO2.
Mentions: Figure 2 shows further structural feature of the hierarchical Li4Ti5O12/TiO2 tubes. A schematic illustration of the individual nanoflake is drawn to show the regions revealed by the HRTEM observation (Figure 2a). The HRTEM image of the nanoflake taken in region I clearly exhibits a periodic arrangement of fringes with an average distance of approximately 1.7 nm, obviously larger than the lattice fringe spacings of Li4Ti5O12 and TiO2 (Figure 2b). The lattice-fringe-like periodic pattern is believed to be derived from defects, demonstrating the regular structural imperfection of these nanoflakes. However, the corresponding selected area electron diffraction (SAED) (inset in Figure 2b) along the [011] zone axis (perpendicular to the nanoflake surface) exhibits a series of spot pattern, characteristic for a single-crystal-like structure. All of the diffraction spots can be well indexed to the spinel Li4Ti5O12 with a cubic structure in which the direction [hkl] is perpendicular to the (hkl) plane. Therefore, it can be concluded that the Li4Ti5O12 nanoflakes are bound by (011) facets on both the top and bottom surfaces. The HRTEM images (Figure 2c, d) of the nanoflake in region I and II are taken along the direction that almost parallels with the nanoflake plane. As shown in Figure 2c, the lattice fringes with a spacing of 0.50 nm attributing to the (111) plane of spinel Li4Ti5O12 with a lattice fluctuation are clearly observed. A careful examination of the HRTEM image indicates that structural imperfection is derived from the interlacing of two or three closely packed parallel (111) planes. This layer-by-layer-like stacking can be clearly observed in the TEM images viewing along or perpendicular to the surface of the nanoflakes (Figure 2d, e). The interlayer spacing of the lattice-fringe-like structural imperfection is approximately 1.7 nm, consistent with that observed in Figure 2b. For a cubic structure, the dihedral angle between the (111) planes is 70.5°. Distinct lattice fringes with a distance of approximately 0.48 nm are observed, corresponding to the (111) planes of spinel Li4Ti5O12 (Figure 2e). The angle between these lattice fringes is approximately 70.5°, consistent with the cubic structure of Li4Ti5O12. It is interesting that plenty of grain boundaries exist among the crystalline domains in the nanoflakes (Figure 2f). These attractive grain boundaries are expected to provide extra diffusion path and storage sites for lithium ions. Figure 2g shows the HRTEM image taken in region III, the root section of the nanoflake. The lattice fringe spacings of 0.49 and 0.36 nm observed are ascribed to the (111) plane of spinel Li4Ti5O12 and (101) plane of anatase TiO2, respectively, confirming the co-existence of the spinel Li4Ti5O12 and anatase TiO2. In addition, a great deal of grain boundaries among the spinel Li4Ti5O12 and anatase TiO2 are also observed in the region. The HRTEM observation is in agreement with that of the XRD analysis. The presence Li4Ti5O12 and TiO2 dual phase significantly increases the grain boundary density.

Bottom Line: Hierarchical Li4Ti5O12/TiO2 tubes composed of ultrathin nanoflakes have been successfully fabricated via the calcination of the hydrothermal product of a porous amorphous TiO2 precursor and lithium hydroxide monohydrate.The regular structural imperfection existed in the nanoflakes also benefit to lithium ion storage property of these tubes.The hierarchical Li4Ti5O12/TiO2 tubes are a promising anode material for lithium-ion batteries with high power and energy densities.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.

ABSTRACT
Hierarchical Li4Ti5O12/TiO2 tubes composed of ultrathin nanoflakes have been successfully fabricated via the calcination of the hydrothermal product of a porous amorphous TiO2 precursor and lithium hydroxide monohydrate. The hierarchical tubes are characterized by powder X-ray diffraction, nitrogen adsorption/desorption, scanning electron microscopy and transmission electron microscopy techniques. These nanoflakes exhibit a quite complex submicroscopic structure with regular structural imperfection, including a huge number of grain boundaries and dislocations. The lithium ion storage property of these tubes is evaluated by galvanostatic discharge/charge experiment. The product shows initial discharge capacities of 420, 225, and 160 mAh g(-1) at 0.01, 0.1, and 1.0 A g(-1), respectively. After 100 cycles, the discharge capacity is 139 mAh g(-1) at 1.0 A g(-1) with a capacity retention of 87%, demonstrating good high-rate performance and good cycleability. The high electrochemical performance is attributed to unique structure and morphology of the tubes. The regular structural imperfection existed in the nanoflakes also benefit to lithium ion storage property of these tubes. The hierarchical Li4Ti5O12/TiO2 tubes are a promising anode material for lithium-ion batteries with high power and energy densities.

No MeSH data available.


Related in: MedlinePlus