ADDITIVES FOR HIGH VOLTAGE LITHIUM-ION BATTERIES

Abstract

Li-ion batteries operating at higher voltages can deliver higher energy densities, which are useful for EV applications. The use of additives that can enable cell operation at high voltages and passivate the electrodes is an effective strategy to address these issues. Ethylene Sulfate (DTD) is a known positive and negative electrode passivating additive. This work investigates various DTD-derivative additives for high voltage applications. The DTD-derivative additives stand out for high voltage operation. However, the cells used contained Polyethylene Terephthalate (PET) tape, which, in the presence of some solvent decomposition products, can break down into a shuttle molecule, Dimethyl Terephthalate (DMT), causing self-discharge in these cells. DMT, however, was found to oxidize when held at high voltages and was tested as a co-additive with Fluoroethylene Carbonate (FEC). The use of these additives would delay any surface reconstruction and solvent consumption occurring in these high voltage cells, enabling longer cycle life.