3-Chloroanisole for overcharge protection of a Li-ion cell

We observed that 3-chloroanisole (3CA), as an electrolyte additive was very effective for overcharging protection during a 12 V overcharging reaction. During overcharging, the cell voltage did not increase beyond 5.3 V, as opposed to other aromatic compounds that showed a voltage shoot-up to 12 V. This behavior was due to the 3CA decomposition and the formation of conducting polymer film within separator and at cathode/electrolyte interface, which consumes the surplus current and inhibit the voltage increase through the shunting effect. In addition, the use of 3CA did not lead to any problems with rate capability, cycle life, and long-term storage behavior at 50 and 70 degrees C. Furthermore, during storage at 90 degrees C for 4 and 24 h, electrolyte with 3CA in a Li-ion cell showed a similar increase of cell thickness as a cell without 3CA. (c) 2007 Elsevier Ltd. All rights reserved.