Browsing by Author "Kim, Youngsik"

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    AQUEOUS LIQUID SOLUTIONS FOR LI-LIQUID BATTERY
    (Office of the Vice Chancellor for Research, 2012-04-13) Salim, Jason; Cheah, Seong Shen; Lee, Wen Chao; Mahootcheian Asl, Nina; Chen, Rongrong; Kim, Youngsik
    The evolvement of Lithium-ion battery industries has begun to carry the industries to step in a new revolution. Consequently, high demand in high energy density batteries in many electronic and electrical appliances, espe-cially energy storage industries been emerged. This new type of batteries has been in extensive research, such as lithium-water battery. Lithium-water battery is a newly developed battery with lithium as the anode and water as the cathode. Lithium is known as one of the most reac-tive metals in periodic table. Therefore, rigorous reaction will be observed when lithium is reacted with water and hence potentially providing an ex-tremely high energy density. This rigorous reaction can be converted into electrical energy and can be stored in a cell. Lithium-water battery is novel and hence, there is no standardized design. In this presentation, lithium anode is separated from water by liquid electrolyte and a ceramic solid electrolyte. The glass-ceramic solid electro-lyte which has Li1.3Ti1.7Al0.3(PO4)3 composition plays an important role of the design of this lithium–water battery. The main purpose of the solid electro-lyte is to separate water from lithium, avoiding a dangerous exothermic re-action. Also, the presence of the super-ionic conductor ceramic can provide very high lithium ion conductivity. The different sizes of solid electrolytes were used in designing Li-liquid battery cell. The effect of the electrolyte size on the voltage of the cell was studied to optimize the cell design. Then, the aqueous solutions containing different chemicals were tested as the liquid cathodes, and their electro-chemical performance were compared to those of the pure DI water. Further results will be presented in the poster presentation.
  • Thumbnail Image
    Item
    CHEMICAL AND PHASE TRANSFORMATION FROM VANADIUM SULFIDE TO OXIDE VIA A NEW CHEMICAL ROUTE FOR THE SYNTHESIS OF Βʹ-LIXV2O5 AS A HIGH PERFORMANCE CATHODE
    (Office of the Vice Chancellor for Research, 2014-04-11) Lee, Wen Chao; Mahootcheian Asl, Nina; Kim, Youngsik; Zhu, Likun
    The used of rechargeable lithium ion batteries are so widely nowadays on consumer electronics especially portable devices such as cellphones, laptops and etc. The advancement of technology has created batteries with providing high energy density without memory effect and minimum the self-discharge on standby mode. Even with these features, researchers are still trying to improve the batteries with more energy density, low cost, better safety and high durability. The energy density improves with high operation voltage and high capacity. All these features came from one source, material. The resources for current commercial cathode material are decreasing and so new alternative cathode with high performance is needed to replace the commercial cathode in the future. The high temperature vanadium pentoxide phase, βʹ-LixV2O5, was synthesized via a new chemical synthesis involving the evolution of vanadium oxides from the 600°C heat treatment of the pure LiVS2 in air. By employing this method of synthesis, well-crystalized, rod-shaped βʹ-LixV2O5 particles 20 – 30 μm in length and 3 – 6 μm in width were obtained. Moreover, the surface of βʹ-LixV2O5 particles was found to be coated by an amorphous vanadium oxysulfide film (~20 nm in thickness). In contrast to a low temperature vanadium pentoxide phase (LixV2O5), the electrochemical intercalation of lithium into the βʹ-LixV2O5 was fully reversible where 0.0 < x < 2.0, and it delivered a capacity of 310 mAh/g at a current rate of 0.07 C between 1.5 V and 4 V. Good capacity retention of more than 88% was also observed after 50 cycles even at a higher current rate of 2 C.
  • Thumbnail Image
    Item
    Design of multilayer electrolyte for next generation lithium batteries
    (2013-05) Mahootcheian Asl, Nina; Kim, Youngsik; El-Mounayri, Hazim; Zhu, Likun; Chen, Jie
    Rechargeable lithium ion batteries are widely used in portable consumer electronics such as cellphones, laptops, etc. These batteries are capable to provide high energy density with no memory effect and they have small self-discharge when they are not in use, which increases their potential for future electric vehicles. Investigators are attempting to improve the performance of these cells by focusing on the energy density, cost, safety, and durability. The energy density improves with high operation voltage and high capacity. Before any further development of high voltage materials, safe electrolytes with high ionic conductivity, wide electrochemical window, and high stability with both electrodes need to be developed. In this thesis a new strategy was investigated to develop electrolytes that can contribute to the further development of battery technology. The first study is focused on preparing a hybrid electrolyte, the combination of inorganic solid and organic liquid, for lithium based rechargeable batteries to illustrate the effect of electrode/electrolyte interfacing on electrochemical performance. This system behaves as a self-safety device at higher temperatures and provides better performance in comparison with the solid electrolyte cell, and it is also competitive with the pure liquid electrolyte cell. Then a multilayer electrolyte cell (MEC) was designed and developed as a new tool for investigating electrode/electrolyte interfacial reactions in a battery system. The MEC consists of two liquid electrolytes (L.E.) separated by a solid electrolyte (S.E.) which prevents electrolyte crossover while selectively transporting Li+ ions. The MEC successfully reproduced the performance of LiFePO4 comparable with that obtained from coin cells. In addition, the origin of capacity fading in LiNi0.5Mn1.5O4full-cell (with graphite negative electrode) was studied using the MEC. The performance of LiNi0.5Mn1.5O4 MEC full-cell was superior to that of coin full-cell by eliminating the Mn dissolution problem on graphite negative electrode as evidenced by transmission electron microscopy (TEM) analysis. The MEC can be a strong tool for identifying the electrochemical performances of future high voltage positive electrode materials and their electrode/electrolyte interfacial reactions. Finally, by employing the multilayer electrolyte concept, a new application will be introduced to recycle the lithium. This study demonstrates the feasibility of using water and the contents of waste Li-ion batteries for the electrodes in a Li-liquid battery system. Li metal was collected electrochemically from a waste Li-ion battery containing Li-ion source materials from the battery’s anode, cathode, and electrolyte, thereby recycling the Li contained in the waste battery at the room temperature.
  • Thumbnail Image
    Item
    Geometric Characteristics of Lithium Ion Battery Electrodes with Different Packing Densities
    (Office of the Vice Chancellor for Research, 2015-04-17) Lim, Cheolwoong; Lee, Wen Chao; Bo, Yan; Song, Zhibin; De Andrade, Vincent; De Carlo, Francesco; Kim, Youngsik; Zhu, Likun
    The microstructure of electrodes plays a critical role in determining the performance of lithium ion batteries (LIBs), because the microstructure can affect the transport and electrochemical processes within electrodes (1-3). Increasing the volume fraction of active materials in the electrode will increase the energy density. However, the electrodes’ structural properties could also be changed significantly and the critical physical and electrochemical processes in LIBs will be affected. Therefore, the performance of a LIB can be optimized for a specific operating condition by designing electrode microstructures. For instance, Hellweg suggested a spatially varying porous electrode model to improve lithium ion transport in electrolyte phase at high charge/discharge rates (4). He showed that the power density of the graded porosity electrode was higher than a homogeneous porosity electrode without energy loss. In this study, we investigate the realistic geometric characteristics of electrode microstructures under different packing densities and the effect of packing density on the performance of LIBs. Moreover, a spatially varying porous electrode will be studied to increase the electrode energy density without losing rate capability. To investigate geometric characteristics of porous microstructures, cathode electrodes were fabricated from a 94:3:3 (weight %) mixture of LiCoO2 (average particle radius = 5 μm), PVDF, and super-P carbon black. To change the packing density, initial thickness of the electrodes was set in a range of 40 ~ 80 μm. Then all electrodes were pressed down to 40 μm by using a rolling press machine. A synchrotron X-ray nano-computed tomography instrument (nano-CT) at the Advanced Phothon Source of Argonne National Lab was employed to obtain morphological data of the electrodes, with a spatial resolution of 60 nm. The morphology data sets were quantitatively analyzed to characterize their geometric properties. Fig. 1 shows the porosity (ε), specific surface area (As, μm-1), tortuosity (τ), and pore size distribution of 4 different electrode microstructures. The pore size distribution of the un-pressed electrode (ε =0.56, black color) demonstrates nonuniformly dispersed active material. The highest packing density electrode (ε =0.36, red color) shows the highest tortuosity. The charge/discharge experiments were also conducted for these 4 different electrodes. The geometric properties and cell testing results will be analyzed and reported. Acknowledgments: This work was supported by US National Science Foundation under Grant No. 1335850. Fig. 1 Geometric characteristics (porosity ε, specific surface area As, tortuosity τ, pore size distribution) of xray generated porous electrode microstructure with different packing densities.
  • Thumbnail Image
    Item
    LITHIUM-AQUEOUS BATTERY
    (Office of the Vice Chancellor for Research, 2012-04-13) Cavazos, Ana; Mosier, Luke; Chen, Rongrong; Kim, Youngsik
    Due to the exceptionally high energy density Lithium-water batteries have very high storage efficiency. Being able to store more energy is im-portant to many industries including electronics and electric vehicles. This is the reason that much research is being done to optimize and explore new techniques of development for these batteries. The Li-water battery has been designed in this project to test water and other aqueous solutions as the cathode. The lithium in a non-aqueous elec-trolyte acts as the anode of the battery. The solid electrolyte used in the lith-ium water batteries is a glass/ceramic (LISICON). The solid electrolyte acts as a separator allowing the Lithium ions to pass through it without allowing the liquid cathode come into direct contact the Lithium. This paper describes the creation and testing of a Lithium-water battery which uses water and Copper (II) Nitrate as the cathode electrolyte. The purpose of this paper is to compare and contrast the difference in voltage of distilled water and distilled water with Copper (II) Nitrate additives as cath-ode. When the tests were conducted, it was found that Copper (II) Nitrate does in fact increase the voltage of the Lithium-water batteries significantly when compared to the distilled water. These results were expected because of Copper (II) Nitrate’s strong electrolyte properties.
  • Thumbnail Image
    Item
    Mathematical analysis of the lithium ion transport in lithium ion batteries using three dimensional reconstructed electrodes
    (2012-05) Lim, Cheol Woong; Zhu, Likun; Xie, Jian; Kim, Youngsik; Anwar, Sohel
    Computational analysis of lithium ion batteries has been improved since Newman and et al. suggested the porous electrode theory. It assumed the electrode as a simple structure of homogeneous spherical particles. Bruggeman relationship which characterizes porous material by a simple equation was adopted in the homogeneous electrode model instead of the electrode morphology. To improve the prediction of a cell performance, the numerical analysis requires the realistic microstructure of the cell. Based on the experimentally determined microstructure of the positive and negative electrodes of a lithium ion battery (LIB) using x-ray micro/nano-CT technology, three dimensional (3D) simulations have been presented in this research. Tortuosity of the microstructures has been calculated by a linear diffusion equation to characterize the 3D morphology. The obtained tortuosity and porosity results pointed out that the Bruggeman relationship is not sufficiently estimate the tortuosity by the porosity of electrodes. We studied the diffusion-induced stress numerically based on realistic morphology of reconstructed particles during the lithium ion intercalation process. Diffusion-induced stresses were simulated at different C rates under galvonostatic conditions and compared with spherical particles. The simulation results showed that the intercalation stresses of particles depend on their geometric characteristics. The highest von Mises stress and tresca stress in a real particle are several times higher than the stresses in a spherical particle with the same volume. With the reconstructed positive electrode structure, local effects in the LIB cathode electrode during galvanostatic discharge process have been studied. The simulation results reported that large current density usually occurs at the joints between cathode active material particles and in the small channels in electrolyte, which will generate high electric joule power. By using the 3D real image of a LIB cathode electrode, numerical simulation results revealed that the spatial distribution of variable fields such as concentration, voltage, reaction rate, overpotential, and etc. in the cathode electrode are complicated and non-uniform, especially at high discharge rates.
  • Thumbnail Image
    Item
    Waste-Lithium-Liquid (WLL) Flow Battery for Stationary Energy Storage Applications
    (Office of the Vice Chancellor for Research, 2013-04-05) Kim, Youngsik; Mahootcheian Asl, Nina
    With using a multi-layer electrolyte that consists of one liquid electrolyte and one solid electrolyte, the choices for cathode will be dramatically widened to include solid, liquid, and gas phases. Applying this concept, gas and liquid phases have been used as cathodes to create different battery systems such as the Li-air, Li-sea water, and Li-aqueous liquid batteries. Based on these reports, we hypothesized that, by charging the cell, Li metal could be electrochemically collected from any material containing Li-ions. This idea extended to harvesting Li metal from waste Li-ion batteries, in both solid and liquid phases, that contain Li-ion sources such as the LixC6 anode, LixFePO4 cathode, and LiPF6 in the EC:DEC electrolyte. The harvested Li metal could then be an energy source for Li-Liquid flow batteries by using water as the cathode. This study demonstrates the feasibility of using waste Li-ion batteries and water for the electrodes in a Waste-Lithium-Liquid (WLL) flow battery that can be used in a stationary energy storage application. Li metal was collected electrochemically from a waste Li-ion battery containing Li-ion source materials from the battery’s anode, cathode, and electrolyte, thereby recycling the Li contained in the waste battery. The harvested Li metal in the battery system was discharged to produce the electricity by using water as the cathode. The discharge voltage of the water showed 2.7 V at 0.1 mA/cm2 versus Li metal harvested from waste Li-ion batteries, compared to 2.8 V versus fresh Li metal at the same current rate. Since the energy source for this proposed battery system is provided by waste Li-ion batteries and water, the cost of the battery dramatically decreases, which is an attractive strategy for a large size energy storage application