A Dual-phasic Carbon Composite Cathode for Lithium-Oxygen Batteries

( Pham Thi Thu Hien ),김영수,이종원,박민식 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

Lithium-oxygen batteries have been attracting a lot of interest due to their extremely huge theoretical capacity. Lithium ion from the anode is combined with reduced oxygen and form lithium peroxide (Li₂O₂) at the cathode during the discharge. Li₂O₂ is stored there and later convert back to lithium ion and oxygen during the charge. Therefore, the cathode should have large surface area to provide abundant reaction sites and large volume to accommodate as much Li₂O₂ as possible. It also should be porous for oxygen transport facilitation and good at electric conductivity. Herein, we propose a dual-phasic carbon composite that exploits the synergy between metal-organic frameworks (MOFs) and carbon nanotubes (CNTs). The dual-phasic nanoarchitecture incorporates the advantages of both components: MOF-C provides a large surface area and a large pore volume for Li₂O₂ storage, and CNTs provide facile pathways for electron and O₂ transport as well as additional spaces for Li₂O₂ storage.

Solution-Processed Inorganic Thin Film Transistors Fabricated from Butylamine-Capped Indium-Doped Zinc Oxide Nanocrystals

Hien Thu Pham,Hyun-Dam Jeong 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.2

Indium-doped zinc oxide nanocrystals (IZO NCs), capped with stearic acid (SA) of different sizes, were synthesized using a hot injection method in a noncoordinating solvent 1-octadecene (ODE). The ligand exchange process was employed to modify the surface of IZO NCs by replacing the longer-chain ligand of stearic acid with the shorter-chain ligand of butylamine (BA). It should be noted that the ligand-exchange percentage was observed to be 75%. The change of particle size, morphology, and crystal structures were obtained using a field emission scanning electron microscope (FE-SEM) and X-ray diffraction pattern results. In our study, the 5 nm and 10 nm IZO NCs capped with stearic acid (SA-IZO) were ligand-exchanged with butylamine (BA), and were then spin-coated on a thermal oxide (SiO2) gate insulator to fabricate a thin film transistor (TFT) device. The films were then annealed at various temperatures: 350 °C, 400 °C, 500 °C, and 600 °C. All samples showed semiconducting behavior and exhibited n-channel TFT. Curing temperature dependent on mobility was observed. Interestingly, mobility decreases with the increasing size of NCs from 5 to 10 nm. Miller-Abrahams hopping formalism was employed to explain the hopping mechanism insight our IZO NC films. By focusing on the effect of size, different curing temperatures, electron coupling, tunneling rate, and inter-NC separation, we found that the decrease in electron mobility for larger NCs was due to smaller electronic coupling.

Solution-Processed Inorganic Thin Film Transistors Fabricated from Butylamine-Capped Indium-Doped Zinc Oxide Nanocrystals

Pham, Hien Thu,Jeong, Hyun-Dam Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.2

Indium-doped zinc oxide nanocrystals (IZO NCs), capped with stearic acid (SA) of different sizes, were synthesized using a hot injection method in a noncoordinating solvent 1-octadecene (ODE). The ligand exchange process was employed to modify the surface of IZO NCs by replacing the longer-chain ligand of stearic acid with the shorter-chain ligand of butylamine (BA). It should be noted that the ligand-exchange percentage was observed to be 75%. The change of particle size, morphology, and crystal structures were obtained using a field emission scanning electron microscope (FE-SEM) and X-ray diffraction pattern results. In our study, the 5 nm and 10 nm IZO NCs capped with stearic acid (SA-IZO) were ligand-exchanged with butylamine (BA), and were then spin-coated on a thermal oxide ($SiO_2$) gate insulator to fabricate a thin film transistor (TFT) device. The films were then annealed at various temperatures: $350^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$, and $600^{\circ}C$. All samples showed semiconducting behavior and exhibited n-channel TFT. Curing temperature dependent on mobility was observed. Interestingly, mobility decreases with the increasing size of NCs from 5 to 10 nm. Miller-Abrahams hopping formalism was employed to explain the hopping mechanism insight our IZO NC films. By focusing on the effect of size, different curing temperatures, electron coupling, tunneling rate, and inter-NC separation, we found that the decrease in electron mobility for larger NCs was due to smaller electronic coupling.

Non-monotonic Size Dependence of Electron Mobility in Indium Oxide Nanocrystals Thin Film Transistor

Pham, Hien Thu,Jeong, Hyun-Dam Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.8

Indium oxide nanocrystals ($In_2O_3$ NCs) with sizes of 5.5 nm-10 nm were synthesized by hot injection of the mixture precursors, indium acetate and oleic acid, into alcohol solution (1-octadecanol and 1-octadecence mixture). Field emission transmission electron microscopy (FE-TEM), High resolution X-Ray diffraction (X-ray), Nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FT-IR) were employed to investigate the size, surface molecular structure, and crystallinity of the synthesized $In_2O_3$ NCs. When covered by oleic acid as a capping group, the $In_2O_3$ NCs had a high crystallinity with a cubic structure, demonstrating a narrow size distribution. A high mobility of $2.51cm^2/V{\cdot}s$ and an on/off current ratio of about $1.0{\times}10^3$ were observed with an $In_2O_3$ NCs thin film transistor (TFT) device, where the channel layer of $In_2O_3$ NCs thin films were formed by a solution process of spin coating, cured at a relatively low temperature, $350^{\circ}C$. A size-dependent, non-monotonic trend on electron mobility was distinctly observed: the electron mobility increased from $0.43cm^2/V{\cdot}s$ for NCs with a 5.5 nm diameter to $2.51cm^2/V{\cdot}s$ for NCs with a diameter of 7.1 nm, and then decreased for NCs larger than 7.1 nm. This phenomenon is clearly explained by the combination of a smaller number of hops, a decrease in charging energy, and a decrease in electronic coupling with the increasing NC size, where the crossover diameter is estimated to be 7.1 nm. The decrease in electronic coupling proved to be the decisive factor giving rise to the decrease in the mobility associated with increasing size in the larger NCs above the crossover diameter.

Non-monotonic Size Dependence of Electron Mobility in Indium Oxide Nanocrystals Thin Film Transistor

Hien Thu Pham,Hyun-Dam Jeong 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.8

Indium oxide nanocrystals (In2O3 NCs) with sizes of 5.5 nm–10 nm were synthesized by hot injection of the mixture precursors, indium acetate and oleic acid, into alcohol solution (1-octadecanol and 1-octadecence mixture). Field emission transmission electron microscopy (FE-TEM), High resolution X-Ray diffraction (Xray), Nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FT–IR) were employed to investigate the size, surface molecular structure, and crystallinity of the synthesized In2O3 NCs. When covered by oleic acid as a capping group, the In2O3 NCs had a high crystallinity with a cubic structure, demonstrating a narrow size distribution. A high mobility of 2.51 cm2/V·s and an on/off current ratio of about 1.0 × 103 were observed with an In2O3 NCs thin film transistor (TFT) device, where the channel layer of In2O3 NCs thin films were formed by a solution process of spin coating, cured at a relatively low temperature, 350 °C. A size-dependent, non-monotonic trend on electron mobility was distinctly observed: the electron mobility increased from 0.43 cm2/V·s for NCs with a 5.5 nm diameter to 2.51 cm2/V·s for NCs with a diameter of 7.1 nm, and then decreased for NCs larger than 7.1 nm. This phenomenon is clearly explained by the combination of a smaller number of hops, a decrease in charging energy, and a decrease in electronic coupling with the increasing NC size, where the crossover diameter is estimated to be 7.1 nm. The decrease in electronic coupling proved to be the decisive factor giving rise to the decrease in the mobility associated with increasing size in the larger NCs above the crossover diameter.

In2O3 nanocrystal–π conjugated molecule hybrid materials for high-capacity anode in lithium ion battery

Hien Thu Pham,이돈성,Tung Duy Dao,정현담 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.57 No.-

Novel approach to fabricate In2O3 nanocrystal (NC)–π conjugated molecule 4,4′-ethyne-1,2-diyldibenzoic acid (EBA) hybrid materials by ligand exchange process, Sonogashira coupling reaction, and their utility as a lithium ion battery anode material have been developed. Here, discharge capacity of 900 mAh g−1, excellent rate performance under ultrahigh current density of 20 C, and initial Coulombic efficiency of 60% at moderate charging/discharging current density of 5 C after 100 cycles have been demonstrated, which are synergistically capable of overcoming the drawback of previous In2O3 material. The π–π network allows fast electron/Li+ transport and significant decrease in interfacial resistance in charge/discharge state.

Temperature -Dependent Charge Transport in Indium Oxide Nanocrystal Thin Fims

Thu-Hien Pham,Hyun-Dam Jeong 한국진공학회 2015 한국진공학회 학술발표회초록집 Vol.2015 No.2

Synthesis of Indium Oxide Nanocrystals Capped by Benzoic Acid via Ligand Exchange Process

Hien-Thu Pham,Ye-Seul Kim,Hyun-Dam Jeong 한국진공학회 2015 한국진공학회 학술발표회초록집 Vol.2015 No.2

Ferroelectric/Dielectric Double Gate Insulator Spin-Coated Using Barium Titanate Nanocrystals for an Indium Oxide Nanocrystal-Based Thin-Film Transistor

Pham, Hien Thu,Yang, Jin Ho,Lee, Don-Sung,Lee, Byoung Hun,Jeong, Hyun-Dam American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.11

<P>Barium titanate nanocrystals (BT NCs) were prepared under solvothermal conditions at 200 degrees C for 24 h. The shape of the BT NCs was tuned from nanodot to nanocube upon changing the polarity of the alcohol solvent, varying the nanosize in the range of 14-22 nm. Oleic acid-passivated NCs showed good solubility in a nonpolar solvent. The effect of size and shape of the BT NCs on the ferroelectric properties was also studied. The maximum polarization value of 7.2 mu C/cm(2) was obtained for the BT-5 NC thin film. Dielectric measurements of the films showed comparable dielectric constant values of BT NCs over 1-100 kHz without significant loss. Furthermore, the bottom gate In2O3 NC thin film transistors exhibited outstanding device performance with a field-effect mobility of 11.1 cm(2)V(-1) s(-1) at a low applied gate voltage with BT-5 NC/SiO2 as the gate dielectric. The low-density trapped state was observed at the interface between the In2O3 NC semiconductor and the BT-5 NCs/SiO2 dielectric film. Furthermore, compensation of the applied gate field by an electric dipole-induced dipole field within the BT-5 NC film was also observed.</P>

In₂O₃ nanocrystal–π conjugated molecule hybrid materials for high-capacity anode in lithium ion battery

Pham, Hien Thu,Lee, Don-Sung,Dao, Tung Duy,Jeong, Hyun-Dam THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.57 No.-

<P><B>Abstract</B></P> <P>Novel approach to fabricate In<SUB>2</SUB>O<SUB>3</SUB> nanocrystal (NC)–π conjugated molecule 4,4′-ethyne-1,2-diyldibenzoic acid (EBA) hybrid materials by ligand exchange process, Sonogashira coupling reaction, and their utility as a lithium ion battery anode material have been developed. Here, discharge capacity of 900mAhg<SUP>−1</SUP>, excellent rate performance under ultrahigh current density of 20C, and initial Coulombic efficiency of 60% at moderate charging/discharging current density of 5C after 100 cycles have been demonstrated, which are synergistically capable of overcoming the drawback of previous In<SUB>2</SUB>O<SUB>3</SUB> material. The π–π network allows fast electron/Li<SUP>+</SUP> transport and significant decrease in interfacial resistance in charge/discharge state.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>