Date of Award

2018

Degree Type

Thesis

Degree Name

Master of Science in Chemistry

Department

Chemistry

First Advisor

Brett L. Lucht

Abstract

Lithium-ion batteries (LIB) are emerging as the energy storage device of choice for vast variety of applications including electric vehicles (EV) and hybrid electric vehicles (HEV). High energy density batteries are in demand to power EVs. The best way to achieve this is the use of high voltage materials. Among all the cathode materials available for LIBs, LiNi0.5Mn1.5O4 (LNMO) with a voltage of 4.75 vs Li/Li+ and a theoretical capacity of 147 mAh/g shows superior properties for high voltage applications. In this study, we used phosphoric acid (PA) modified LNMO electrodes and lithium bis-(oxalato)borate (LiBOB) electrolyte additive separately and together to investigate the cell performance. The cycling data suggested that the PA modification of LNMO significantly improves the performance of LNMO/graphite full cells, which is further enhanced by LiBOB additive in the electrolyte. The metal ion concentrations obtained through ICP-MS studies performed on harvested anodes from cycled cells reveal relatively low levels of manganese and nickel deposited on the anode for PA modified LNMO and cells with LiBOB. The improvement in electrochemical performance is directly related to the reduction in transition metal dissolution. The surface analytical techniques FTIR and XPS have also been performed to further investigate the performance improvement by PA modification and LiBOB.

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