We have studied the thermal stability of NCM622 cathode material for Li-ion batteries using real-time synchrotron x-ray scattering below 600°C in both air and vacuum. The expansion of the mean particle size, which reached maximum values of 10.3 μm in air and 10.6 μm in vacuum at 200°C, was attributed to the dehydration of intergranular water within the NCM622 powders. Across all annealing temperatures, the amount of crystal NCM622 phase in air was consistently higher than that in vacuum. The crystal domain sizes in air showed less variation than that in vacuum during annealing from RT to 500°C. These indicate that the crystal NCM622 phase is more thermally stable during annealing in air than in vacuum. This stability is attributed to the presence of 21% oxygen in air, which is absent under vacuum conditions.
Thermal batteries are designed to activate at high temperatures (~500℃), therefore, the electrodes used in these systems are typically made into pellet form using compression molding techniques that do not involve polymer binders. However, the compression molding technique poses limitations in scaling up the electrode area without increasing thickness for high-power properties. Additionally, the tape casting method has been studied as a way to solve with, but too low a loading level is still an obstacle to practical use. This study fabricated a film cathode of high loading level (35.79 mAh·cm-2) using the tape casting method for these problem. As utilized fabricated cathode, it investigated the influence of electrode thickness and density on electrochemical performance. Furthermore, a film cathode with a larger area but the same amount of active material as the pellet was fabricated, enabling the design of high-power cells with the same energy density. We expect that the fabricated film cathode with a high loading level and scalable area will enable the development of various thermal battery designs.
The thermal management issue in OLED (organic light emitting diode) devices has a significant impact on the efficiency, reliability, and life time of the device. In particular, in OLED systems with multipolar or double cathode electrodes, it is important to accurately interpret the effect of heat generated by current flow between electrodes on the emitting layer. In this study, the governing equation was established based on the heat conduction equation to mathematically model and analyze this heat distribution, and the heat distribution analysis was performed using the COMSOL program. It was confirmed that the temperature generated in the OLED with the double cathode structure reached a maximum of 343.157 K centered on the emitting layer. The heat distribution generated in the proposed OLED structure with the double cathode electrodes was confirmed to be highly distributed in the center toward the double cathode electrodes, which is believed to be because the arrangement of the double cathode electrodes improves the symmetrical distribution of temperature while reducing power consumption.
Ni-rich cathode materials have been developed as the most promising candidates for next-generation cathode materials for lithium-ion batteries because of their high capacity and energy density. In particular, the electrochemical performance of lithium-ion batteries could be enhanced by increasing the contents of nickel ion. However, there are still limitations, such as low structural stability, cation mixing, low capacity retention and poor rate capability. Herein, we have successfully developed the nanorod-type Ni-rich cathode materials by using co-precipitation method. Particularly, the nanorod-type primary particles of LiNi0.7Co0.15Mn0.15O2 could facilitate the electron transfer because of their longitudinal morphology. Moreover, there were holes at the center of secondary particles, resulting in high permeability of the electrolyte. Lithium-ion batteries using the prepared nanorod-type LiNi0.7Co0.15Mn0.15O2 achieved highly improved electrochemical performance with a superior rate capability during battery cycling.
To overcome the limitations of the conventional Ni anode-supported SOFCs, various types of ceramic anodes have been studied. However, these ceramic anodes are difficult to commercialize because of their low cell performances and difficulty in manufacturing anode-support typed SOFCs. Therefore, in this study, to use these ceramic anodes and take advantage of anode-supported SOFC, which can minimize ohmic loss from the thin electrolyte, we fabricated cathode support-typed SOFC. The cathode-support of LSCF-YSZ was prepared by the acid treatment of conventional Ni-YSZ (Yttria-stabilized Zirconia) anode-support, followed by the infiltration of LSCF to YSZ scaffold. The composite of La(Sr)Ti(Ni)O3 and Ce(Mn, Fe)O2 was used as the ceramic anode. The fabricated cathode-supported button cell showed a relatively low power density of 0.207 Wcm-2 at 850℃; however, it is expected to show better performance through the optimization of the infiltration rate and thickness of LSCF-YSZ cathode-support layer.
Thermal batteries are used in military power sources that require robustness and long storage life for applications in missiles and torpedoes. FeS2 powder is currently used as a cathode material because of its high specific energy density, environmental non-toxicity, and low cost. MS2 (M = Fe, Ni, Co) cathodes have been explored as novel candidates for thermal batteries in many studies; however, the discharge characteristics (1, 2, 3 plateau) of single cells in thermal batteries with different cathodes have not been elucidated in detail. In this study, we independently analyzed the discharge voltage and calculated the total polarizations of single cells using MS2 cathodes. Based on the results of this study, we propose NiS2 as a potential cathode material for use in thermal batteries.
In this study, Li2MnSiO4 cathode material and LiPON solid electrolyte were manufactured into thin films, and the possibility of their use in thin-film batteries was researched. When the RTP treatment was performed after Li2MnSiO4 cathode thin-film deposition on the SUS substrate by a sputtering method, a β-Li2MnSiO4 cathode thin film was successfully manufactured. The LiPON solid electrolyte was prepared by a reactive sputtering method using a Li3PO4 target and N2 gas, and a homogeneous and flat thin film was deposited on a Li2MnSiO4 cathode thin film. In order to evaluate the electrochemical properties of the Li2MnSiO4 cathode thin films, coin cells using only a liquid electrolyte were prepared and the charge/discharge test was conducted. As a result, the amorphous thin film of RTP treated at 600℃ showed the highest initial discharge capacity of about 60 μAh/㎠. In cases of coin cells using liquid/solid double electrolyte, the discharge capacities of the Li2MnSiO4 cathode thin films were comparable to those without solid LiPON electrolyte. It was revealed that Li2MnSiO4 cathode thin films with LiPON solid electrolyte were applicable in thin film batteries.
Powder compaction technology is widely used to prepare thermal battery components. This method, however, is limited by the size, thickness, and geometry of the battery components. This limitation leads to excessive cell capacity, overweight, and higher cost of the pellets, which decreases the specific capacities and delays the activation time of thermal batteries. FeS2 thin-film cathodes were fabricated by tape-casting technology and analyzed by SEM and EDS in this paper. The residual organic binder of the FeS2 thin-film cathodes decreased with the temperature of the heat treatment, which improved the specific capacity because of the lower resistance. Specific capacities of the FeS2 thin-film cathodes decreased because of the higher residual binder and the restrictive reaction of active materials with molten salts as the thickness increased. FeS2 thin-film cathodes showed much higher specific capacity (1,212.2 As/g) than pellet cathodes (860.7 As/g) at the optimal heat-treatment temperature (230℃).
Cs3Sb photocathode was formed by newly developed process and successive in-situ lightingdevices were fabricated in a process chamber. R, G, and B phosphors were applied on the anode plate,respectively. Major parameters such as brightness, power consumption, and efficacy were measured. Thewavelength of LED excitation source was 450 nm. Both high power and low power modes were appliedin the measurement. Measurement values were clearly differentiated by the voltage application modes. The measured values of each parameter was good enough to be applied for general lighting source. Theresults showed that Cs3Sb photocathode formed in atmospheric conditions was functioning as good as thephotocathode formed in UHV conditions, and thus it could be applied to advanced lighting devices.
Photoemission is a process in which photons are converted into free electrons. Photocathodesare the typical materials for the process. They emit electrons when a light is irradiated upon. Thetraditional method of manufacturing photocathodes is complicated, requires specialized equipment, and islimited very small sized samples. Cs3Sb photocathode was formed on a substrate in atmosphericconditions. The photocathode formation was a gas phase reaction with the substrate. Vacuum deviceswere made to test electron emission characteristics of the formed photocathode. Visible light ofwavelength 475 nm was used for the primary light source. The results showed high current density andlong term stability of the photoelectron emission.
Nano-fibers of the Li[Ni1/3Co1/3Mn1/3]O2 electrode were synthesized from a metal oxide precursor using the electrospun method. The XRD patterns of all prepared powders showed a hexagonal α- NaFeO2 structure (space group: R-3 m, 166). Scanning electron microscopy showed that all the synthesized samples were comprised of nanofibers with a size of 100~800 nm. Among the samples tested, the calcined Li[Ni1/3Co1/3Mn1/3]O2 nanowires in oxygen heating atmosphere showed a high charge and discharge capacity of 239.22 and 172.81 mAhg-1 at the 1st cycle, respectively. In addition, the charge transfer resistance was also improved significantly compared to the other samples.
In this study, magnesium (Mg), zinc (Zn) and aluminium (Al) as anode electrode and the solution of NaCl dissolved with 2~20 wt% as electrolytes were used for the metal-air cell. The open circuit voltage, short circuit current and I-V characteristics upon different kinds of anode electrode and electrolyte concentration were investigated. The open circuit voltage, initially about 1.45 V, rises to 1.6 V during the first 10 minutes indicating the necessity of an induction time to activate the catalyst on the air cathode. The short circuit current increases with an increased concentration of NaCl, causes an increase in the conductivity of the electrolyte solution, but the open circuit voltage did not under undergo influence of electrolyte. From NaCl 20 wt% electrolyte, the maximum output power of the magnesium electrode materials was measured with 177mW. It is found that the power characteristics of metal-air cell could be improved by using magnesium electrode materials in the NaCl electrolyte.
We fabricated red and blue organic light emitting display (OLEDs) which had the two kinds of multi-structure of ITO/HIL/HTL/EML/ETL/LiF/Al and ITO/HIL/HTL/EML/ETL/LiF/Al/LiF. In the case of red OLED that had LiF/Al/LiF structure compared to LiF/Al structure, the current density increased from 4.3 ㎃/㎠to 7.3 ㎃/㎠, and the brightness increased from 488 ㏅/㎡to 1,023 ㏅/㎡at 7.0 V, and as a result the current efficiency was improved from 11.28 cd/A to 13.95 cd/A. Also in the case of blue OLED that had LiF on Al cathode layer, the current density increased from 1.2 ㎃/㎠to 1.8 ㎃/㎠, and the brightness increased from 45 ㏅/㎡to 85 ㏅/㎡at 7.0 V, and as a result the current efficiency was improved from 3.69 cd/A to 4.82 cd/A. Through these experimental results it could be suggested that the LiF layer formed on Al prevents the oxidation of Al surface, and the electrode resistance become low with increase of supplied electrons, therefore the brightness and the efficiency are improved from the influence to the well-balanced bonding of electron and hole at emitting layer.
We have proposed a new configuration on the cathode structure to improve a neutron yield without the application of external ion sources in an inertial electrostatic confinement (IEC) device. A neutron yield in the IEC device is closely related to the potential well structure generated inside the cathode and is proportional to the ion current. Therefore, the application of a double grid cathode structure to the IEC device is expected to produce a higher ion current and neutron yield than at a single grid cathode due to a high electric field strength generated around the cathode. These possibilities were verified as compared with the ion current calculated from both shape of the single and double grid cathode. Additionally from the results of ion`s lives and trajectories examined at various outer cathode voltages and grid cathode configurations by using particle simulations, the validity of the double grid cathode was confirmed.
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