Iodine as a Temperature-Responsive Redox Shuttle Additive for Swelling Suppression of Lithium-Ion Batteries at Elevated Temperatures

摘要

The swelling issue by gas evolution at elevated temperatures (85-90 degrees C) is one of the major challenges related to current Li-ion batteries (LIBs). We herein demonstrate that iodine (I-2) as a redox shuttle additive, when its dose is properly determined, can suppress the swelling behavior of LiCoO2/graphite Al-pouch cells during storage at 90 degrees C without sacrificing other cell performances. This approach is based on two findings: 1) swelling during 90 degrees C storage is severe only when the cells are fully charged, and 2) the shuttling reaction of I-2 can be tuned to be activated only when the temperature is as high as 90 degrees C by employing an appropriate amount of I-2. Therefore, when a fully charged cell is exposed to a temperature of 90 degrees C, the self-discharge by I-2 lowers the state of charge of the cell, suppressing the swelling. This temperature-responsive shuttling behavior of I-2 is ascribed to the preferential adsorption of I-2 on the cathode surface. It is also confirmed that inclusion of the I-2 additive does not lead to deterioration in other aspects of cell performance, such as the discharge capacity or long-term cyclability. Along with the improved cell performance, the low-cost and environmental compatibility of I-2 makes it a promising electrolyte additive for thermally robust LIBs.