Stability of conductive carbon additives in 5 V-class Li-ion batteries

A high oxidation stability of electrode components, especially of conductive carbon additives, is of importance in order to realize high-voltage (5 V-class) Li-ion batteries with higher energy densities. In this work, the oxidation stability of acetylene blacks is studied by analyzing the capacity (i.e., quantity of electricity) arising from their oxidation reactions via chronopotentiometry up to 5.5 V (vs. Li+/Li) in a highly concentrated electrolyte with high oxidation stability. Annealing at 1200 °C can improve their oxidation stability below 4.8 V by reducing the amounts of surface active sites. However, further raising the annealing temperature significantly degrades the stability at higher potentials (>4.8 V) due to the electrochemical anion intercalation induced by progressive graphitization. This work suggests that, for 5 V-class batteries, conductive carbon additives should be optimized to simultaneously minimize surface active sites and excessive graphitization.