EXPERIMENTAL STUDY OF LITHIUM-ION CELLS WITH HIGH LOADING NMC622 CATHODE AND NMP-FREE PROCESS
Open Access
Author:
Tsai, Ya Chen
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 03, 2019
Committee Members:
Chao-Yang Wang, Thesis Advisor/Co-Advisor
Keywords:
Li-ion battery thick electrode NMP-free
Abstract:
A set of lithium-ion pouch cells consisting of thick NMC622 cathodes with high loading (~21.65 mg/cm2) and graphite anodes (~12.1 mg/cm2) were tested under C/3 and 1C cycling. Three different cathode coatings utilized binder with NMP-free process is developed. The aim of this study is to investigate the cycling performance of such cathodes compared to the baseline cathode with NMP-PVDF binder. NMP-free and NMP-PVDF based cells have discharge capacity retention of 87.9% and 88.7% after 600 cycles, respectively. The cycle life for both groups is expected to reach more than 1000 cycles at C/3 cycling. Fresh and aged cells were characterized by various techniques, including C-rate test, electrochemical impedance spectroscopy (EIS), direct current resistance (DCR) test. The NMP-free cells were found to have larger resistance than the NMP-PVDF cells, and the significant increase of resistance on the cathode side of which also found from the EIS measurement. Moreover, it is found that the rate capability became poor after 600 cycles, especially for cells with NMP-free binder at higher C-rate. Further improvement is required for a high loading lithium-ion battery with the NMP-free binder, focusing on getting high energy density with good rate capability and longer cycle life of LIB.
