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Sanjay Ramdon MS thesis.pdf (3.61 MB)

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Nanoscale Characterization of Aged Li-Ion Battery Cathodes

Ramdon, Sanjay Kiran
http://rave.ohiolink.edu/etdc/view?acc_num=osu1376625747

Abstract Details

2013, Master of Science, Ohio State University, Mechanical Engineering.
Lithium-ion (Li-ion) batteries have become very prominent as a form of energy storage for numerous applications due to its high energy and power densities. They are used for numerous portable devices and more recent electric vehicles (EVs). It is important to increase the cycle life of Li-ion batteries in order for them to be more viable for the automotive industry. With use, these batteries undergo an aging process which reduces the battery storage capacity and increases internal resistance. To reduce the aging process it is essential to first understand the degradation mechanisms on the electrodes of the battery. A multi-scaled approach has been previously applied to the study of the degradation of the LiFePO4 cathodes. It has been shown that nanoparticles in cathodes coarsen as a result of aging. Coarsening of nanoparticles has been shown to lead to an increase in surface resistance and decrease in surface conductivity, which is responsible for reduced lithium retaining capacity. It is therefore important to study the cause of these aging mechanisms in order to increase the life of the battery. An in depth study of cathode on the nanometer scale is necessary using atomic force microscope (AFM) related techniques. In this work, both ex-situ and in-situ studies were conducted to understand the aging phenomenon in LiFePO4 battery cathodes. High resolution AFM imaging and current measurements were conducted to study the difference of the unaged cathode from the aged. This was done to quantify the coarsening process. Particle agglomeration was observed in the aged cathode, which is believed to reduce surface conductivity. Nanomechanical characterization and mechanical integrity studies were then conducted on unaged and aged cathodes using AFM equipped with nanoindentor. This was done to determine the effect of increased internal stress within the cathode created during aging on the nanomechanical and mechanical integrity properties. Properties of hardness, elastic modulus, creep, nanowear, nanoscratch and nanofriction were examined and significant differences were observed between unaged and aged cathodes. The aged cathodes showed higher hardness, creep depth and critical load in scratch and lower wear depth and coefficient of friction. In order to further understand aging mechanisms, real time examination of battery cathodes were done during operation of the cell using in-situ techniques. AFM in-situ techniques allow direct observation of cathodes during cycling of the cell on the nanometer scale. Morphology data showed increase in particle size from FePO4 phase to LiFePO4 phase during discharge of the cell due to lithiation. In-situ AFM electrochemical characterization has been shown to be a useful technique to study Li-ion battery aging mechanisms. These studies further the understanding of the degradation mechanisms of Li-ion battery cathodes. The in situ electrochemistry approach advanced in this work is believed to be useful for fundamental understanding of aging mechanisms.
Bharat Bhushan (Advisor)
96 p.
Mechanical Engineering
Li-Ion, battery, LiFePO4 cathode degradation ,In situ electrochemical cell, aging of cathode, AFM, nanoindentation

Recommended Citations

Citations

  • Ramdon, S. K. (2013). Nanoscale Characterization of Aged Li-Ion Battery Cathodes [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376625747

    APA Style (7th edition)

  • Ramdon, Sanjay. Nanoscale Characterization of Aged Li-Ion Battery Cathodes . 2013. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1376625747.

    MLA Style (8th edition)

  • Ramdon, Sanjay. "Nanoscale Characterization of Aged Li-Ion Battery Cathodes ." Master's thesis, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376625747

    Chicago Manual of Style (17th edition)

osu1376625747
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This open access ETD is published by The Ohio State University and OhioLINK.