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Fabrication and Simulation of Semi-Solid Electrodes for Flexible Lithium-Ion Batteries

Zakri, Waleed
http://rave.ohiolink.edu/etdc/view?acc_num=akron1531480028749308

Abstract Details

2018, Doctor of Philosophy, University of Akron, Mechanical Engineering.
Flexible Li-ion batteries (LIBs) have strong forthcoming consumer market demand for use in different wearable electronic devices, flexible smart electronics, roll-up displays, electronic shelf labels, active radio-frequency identification tags, and implantable medical devices. This market demand necessitates research and development of these batteries in order to fulfill the energy and power requirements of these next-generation devices. In this study, the performance of semi-solid electrodes, which consists of active and conductive additive materials suspended in liquid electrolyte, for flexible LIBs is investigated through experiment and modeling. For the semi-solid graphite anode three different conductive additive materials of Super C45, Super P, and Ketjenblack are investigated. For the liquid electrolyte, which is mixed with graphite and conductive additive materials, lithium hexafluorophosphate salt (LiPF6) was dissolved in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). Several semi-solid graphite anodes with different compositions were fabricated and tested during the study. Over 65% of the specific discharge capacity to the theoretical capacity was achieved for the optimal composition of an anode. The semi-solid lithium cobalt oxide (LCO) cathode was also fabricated and tested simultaneously in the same lab. Subsequently, a full cell for a flexible LIB was fabricated based on the performances of the optimum LCO cathode and graphite anode half cells; then, the full cell was tested using galvanostatic measurements. A specific discharge capacity of over 60 mAh/g based on cathode mass was obtained when the cell was charged and discharged in the voltage range of 2.5-4.2V at a C-rate of C/40. In order to reduce the number of experiments and to achieve the desired energy capacity of the battery, a mathematical model was developed. This model is a multiphysics three-dimensional heterogeneous model. All necessary transport phenomena including the charge and mass transfer and electrochemical reactions are considered at continuum mechanics level in the model. COMSOL Multiphysics software is used to solve governing equations numerically using a finite element method. This model is for a half-cell simulation, and by using experimental results obtained in the lab, this model separately validates both a semi-solid LCO cathode and a semi-solid graphite anode. To achieve the full-cell model, the developed half-cell models were enhanced using the same transport phenomena equations at a continuum mechanics level. Anode and cathode electrodes were modeled to serve as active components of the full-cell while the liquid electrolyte could pass through the void between the particles. The results confirm that both the fabricated and computer simulated full-cell for the flexible LIB are in good agreement with less than 5% error at the end of discharge. After developing the full-cell model, the effect of the cell temperature, the separator thickness, electrodes mass, the discharge current rate, and the initial concentration of hexafluorophosphate salt (LiPF6) in the electrolyte were examined. Lower values of discharge capacity were observed with higher C-rates or larger separator thickness. The cell was also simulated at different cell temperatures confirming that capacity is not strongly affected by temperature, as minor changes were obtained. In order to maximize the capacity, the cell with high anode electrode mass had a higher specific discharge capacity when the cell was simulated at different electrode mass ratio. These simulation results are necessary to save both time and cost of materials, along with components used for fabricating semi-solid electrodes. Overall, the results obtained confirm that the fabrication of a relatively high-energy density of flexible primary LIB, based on the concept of semi-solid electrodes, is feasible and can be used effectively for low power demand applications.
Siamak Farhad, Dr. (Advisor)
Alper Buldum, Dr. (Committee Member)
Yilmaz Sozer, Dr. (Committee Member)
Chen Ling, Dr. (Committee Member)
Kevin Kreider, Dr. (Committee Member)
116 p.
Mechanical Engineering
Lithium-ion batteries; Flexible; Electrode suspension; Graphite; Lithium cobalt oxides; Simulation; Fabrication; heterogeneous

Recommended Citations

Citations

  • Zakri, W. (2018). Fabrication and Simulation of Semi-Solid Electrodes for Flexible Lithium-Ion Batteries [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1531480028749308

    APA Style (7th edition)

  • Zakri, Waleed. Fabrication and Simulation of Semi-Solid Electrodes for Flexible Lithium-Ion Batteries. 2018. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1531480028749308.

    MLA Style (8th edition)

  • Zakri, Waleed. "Fabrication and Simulation of Semi-Solid Electrodes for Flexible Lithium-Ion Batteries." Doctoral dissertation, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1531480028749308

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.
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