Mesoporous Carbon/Li4Ti5O12 Nanoflakes Composite Anode Material Lithiated to 0.01 V (original) (raw)
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Mesoporous carbon–titania nanocomposites for high-power Li-ion battery anode material
Journal of Physics and Chemistry of Solids, 2010
We have investigated the Li-ion battery anode properties of several kinds of mesoporous composites of carbon and titanium dioxides (titania, TiO 2 ) prepared by tri-constituent co-assembly method. The maximum reversible capacity (197 mAh/g) at current density of 50 mA/g was obtained for the composite of TiO 2 :carbon = 7:3 calcined at 600 1C. It was also found that the composite maintained the high reversible capacity as large as 109 mAh/g even at the high current density of 1000 mA/g.
Nanocomposite particles of amorphous carbon-Li4Ti5O12 (C-LTO) and carbon nanotube-Li4Ti5O12 (CNT-LTO) were synthesized by solvothermal method and subsequent high-temperature calcination. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED) were applied to characterize the phase structure, particle morphology, and the coating structure. XRD analysis, TEM micrographs, HR-TEM images and SAED analysis revealed that both LTO particles exhibited a welldeveloped spinel nanocrystal structure with average sizes between 20-70 nm. The C-LTO particles exhibited roughly spherical shape coated by an amorphous carbon layer up to 10 nm in thickness. The CNT-LTO samples showed uniform square nanocrystals with edge length around 20 nm and nanoscale graphitic layers covering the surface, revealing the carbon nanotubes interconnection networks among the particle assemblies. Electrochemical studies of lithium insertion/extraction performance are evaluated by the galvanostatic charge/discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Both LTO particles showed the superior initial discharge capacity of more than 200 mAh/g at 1/10C rate. The irreversible capacity of the C-LTO particles at more cycles was due to large polarization resulted from excessive carbon and possible residual precursors. The CNT-LTO particles show larger reversible capacity and enhanced electrochemical Li+ insertion/extraction kinetics at different cycling rates. The comparative structural and electrochemical analyses demonstrated that both nanoscale graphitic covering layers and the CNT interconnection networks increase the electronic conductivity and improve the kinetics rates of lithium insertion/extraction in the CNT-LTO particles.
Carbon-Encapsulated F-Doped Li4Ti5O12 as a High Rate Anode Material for Li+ Batteries
ACS Nano, 2013
TiO 2 nanoparticles aggregated into a regular ball-inball morphology were synthesized by hydrothermal processing and converted to carbon-encapsulated F-doped Li 4 Ti 5 O 12 (LTO) composites (C-FLTO) by solid state lithiation at high temperatures. Through the careful control of the amount of carbon precursor (D(þ)-glucose monohydrate) used in the process, LTO encapsulated with a continuous layer of nanoscale carbon was formed. The carbon encapsulation served a dual function: preserving the ball-in-ball morphology during the transformation from TiO 2 to LTO and decreasing the external electron transport resistance. The fluoride doping of LTO not only increased the electron conductivity of LTO through trivalent titanium (Ti 3þ) generation, but also increased the robustness of the structure to repeated lithiation and delithiation. The best-performing composite, C-FLTO-2, therefore delivered a very satisfying performance for a LTO anode: a high charge capacity of ∼158 mA h g À1 at the 1 C rate with negligible capacity fading for 200 cycles and an extremely high rate performance up to 140 C.
Li4Ti5O12-coated graphite as an anode material for lithium-ion batteries
Applied Surface Science, 2012
In this study, we have synthesized and characterized Li 4 Ti 5 O 12 (LTO)-coated meso-carbon micro beads (MCMB) as an anode material for Li-batteries. The surface of MCMB powders was uniformly coated by the LTO nanoparticles to form a core-shell structure via a sol-gel process, followed by calcination. The average size of MCMB core was 20 m while the thickness of LTO shell was 80-120 nm. We found that LTOcoated MCMB has better rate-capability and cycle life, compared with the pristine MCMB. Electrochemical impedance spectroscopy (EIS) results showed that after 40 cycles, the cell resistance of the LTO-coated MCMB electrode increased slightly, while that of the pristine MCMB electrode increased significantly. The enhanced performance of the LTO-coated MCMB electrode is attributed to the LTO coating, which suppresses the increase in the charge-transfer resistance during prolonged cycle.
Carbon coated Li4Ti5O12 (C-LTO) particles have been synthesized by hydrothermal method and high-temperature calcination process. Nanostructure and carbon-coating has been characterized in detail by Xray diffraction (XRD), high resolution TEM (HR-TEM), selected electron diffraction (SAED), and scanning transmission X-ray microscopy (STXM) combined with X-ray absorption near edge structure (XANES) spectroscopy. The prepared particles are comprised of highly crystalline spinel-type Li4Ti5O12 with the size range of 20-70 nm. HR-TEM imaging and STXM-XANES spectromicrocopy confirmed the amorphous carbon layer uniformly covered on the surface of single LTO particles with optimized content and coating thickness (~5 nm). The electrochemical performance of C-LTO particles as an anode in lithium-ion batteries is evaluated, demonstrating both improved rate capability and cycling performance, which was attributed to the enhanced electron transport/high electrical conductivity and fast lithium-ion insertion/extraction, as a result of uniform and optimized amorphous carbon coating on the C-LTO particles.
Carbon coated Li 4 Ti 5 O 12 (C-LTO) particles have been synthesized by hydrothermal method and high-temperature calcination process. Nanostructure and carbon-coating has been characterized in detail by Xray diffraction (XRD), high resolution TEM (HR-TEM), selected electron diffraction (SAED), and scanning transmission X-ray microscopy (STXM) combined with X-ray absorption near edge structure (XANES) spectroscopy. The prepared particles are comprised of highly crystalline spinel-type Li 4 Ti 5 O 12 with the size range of 20-70 nm. HR-TEM imaging and STXM-XANES spectromicrocopy confirmed the amorphous carbon layer uniformly covered on the surface of single LTO particles with optimized content and coating thickness (~5 nm). The electrochemical performance of C-LTO particles as an anode in lithium-ion batteries is evaluated, demonstrating both improved rate capability and cycling performance, which was attributed to the enhanced electron transport/high electrical conductivity and fast lithium-ion insertion/extraction, as a result of uniform and optimized amorphous carbon coating on the C-LTO particles.
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Synthesis of composite Li4Ti5O12 nanorods/Sn-AC as anode material for lithium-ion battery
E3S Web of Conferences, 2018
LTO or Li4Ti5O12 (lithium titanate) is a compound that is used as an anode component in a lithium-ion battery. LTO anode is used because it has zero-strain properties and doesn't produce SEI (solid electrolyte interphase) which cause low battery performance. However, LTO also has a problem, which is its low capacity. To overcome this problem, the LTO needs to be combined with other materials that have high capacity, which, in this case, are active carbon (AC) and Sn. Making the LTO to be nano-sized can also improve the performance of the battery, thus we tried to synthesize LTO in nanorods form. LTO nanorods are synthesized by hydrothermal in NaOH 4 M solution. The LTO nanorods are mixed with various Sn (5wt%, 10wt%, and 15wt%) and 5wt% activated carbon. LTO nanorods/Sn-AC composite was characterized using XRD, SEM-EDS, and BET and the battery performance was analyzed by EIS, CV, and CD. The results showed that the highest capacity was obtained at LTO nanorods-AC/15wt% Sn with 1...
Critical Role of the Crystallite Size in Nanostructured Li4Ti5O12 Anodes for Lithium-Ion Batteries
ACS Applied Materials & Interfaces, 2018
Lithium titanate Li 4 Ti 5 O 12 (LTO) is regarded as a promising alternative to carbon-based anodes in lithium-ion batteries. Despite its stable structural framework, LTO exhibits disadvantages such as the sluggish lithium-ion diffusion and poor electronic conductivity. In order to modify the performance of LTO as an anode material, nanosizing constitutes a promising approach, and the impact is studied here by systematical experimental approach. Phase-pure polycrystalline LTO nanoparticles (NPs) with high crystallinity and crystallite sizes ranging from 4 to 12 nm are prepared by an optimized solvothermal protocol and characterized by several state-of-the-art technologies including HRTEM, XRD, PDF (pair distribution function) analysis, Raman spectroscopy and XPS. Through a wide array of electrochemical analyses, including charge/discharge profiles, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), a crystallite size of approx. 7 nm is identified as optimum particle size. Such NPs exhibit as good reversible capacity as the ones with larger crystallite sizes, but a more pronounced interfacial charge storage. By decreasing the crystallite size to about 4 nm the interfacial charge storage increases remarkably, however resulting in a loss of reversible capacity. An in-depth structural characterization using the PDF obtained from synchrotron XRD data indicates an enrichment in Ti for NPs with the small crystallite sizes, and this Ti-rich structure enables a higher Li storage. The electrochemical characterization confirms this result and furthermore points to a plausible reason why a higher Li-storage in very small nanoparticles (4 nm) results in a loss in the reversible capacity.