Separator Oxidation Determination
Publication Date: 2016-Nov-22
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A novel, low cost procedure to detect separator oxidation
Separators in contact with the anode and cathode of a battery experience oxidation and reduction at the surface of each electrode. Polyolefin separators in Li-ion batteries undergo oxidative decomposition due to their low resistance to oxidation. This oxidative decomposition worsens at higher operating temperatures and voltages and eventually reduces cycle life and battery performance. The resistance of separators to oxidation has become increasingly important as the demand for higher-capacity batteries increases. However, the resistance of separators to oxidation has not been actively studied.
Traditional approaches show a method to determine electrochemical stability of a complete cell (and may indirectly or partially measure degree of separator oxidation), either by measuring capacity loss or voltage drop in a cell when exposed to higher than 100% SOC storage voltage and/or elevated temperatures.
New approach - overcharge studies were performed using 1.5 Ah Li-ion LCO/Gr pouch cells and carried out at a 0.5 C charge rate. Following overcharge, the cells were immediately discharged to 0V prior to cell tear down and analysis.
(1) Fig 1 is the FTIR spectra of separators taken directly from the overcharged cells.
(2) 20ml DMC was used to treat the separator to remove the organic solvents (overnight treatment time). The separator was then dried and FTIT analysis was performed. Fig 2 is the FTIR spectra o...