Electronegativity-induced enhancement of thermal stability by succinonitrile as an additive for Li ion batteries

Succinonitrile (SN, CN–[CH2]2–CN) is evaluated as an additive for improving thermal stability in ethylene carbonate (EC)-based electrolytes for lithium ion batteries. Without any sacrifice of performance such as cyclability and capacity, the introduction of SN into an electrolyte with a graphite anode and LixCoO2 cathode leads to (1) reducing the amount of gas emitted at high temperature, (2) increasing the onset temperature of exothermic reactions and (3) decreasing the amount of exothermal heat. The improvement in the thermal stability is considered to be due to strong complex formation between the surface metal atoms of LixCoO2 and nitrile (–CN) groups of SN, from spectroscopic studies based on photoelectrons induced by X-rays and by considering that the exothermic heat and gas evolution are caused by interfacial reactions between the electrolyte and cathode.