Safety Aspects of Graphite Negative Electrode Materials for Lithium-Ion Batteries

Safety aspects of different graphite negative electrode materials for lithium-ion batteries have been investigated using differential scanning calorimetry. Heat evolution was measured for different types of graphitic carbon between 30 and 300°C. This heat evolution, which is irreversible, starts above 100°C. From the values of energy evolved, the temperature rise in complete lithium-ion cells was estimated. The heat evolved between 80 and 220°C is a linear function of the irreversible charge capacity of the carbon. The specific Brunauer, Emmett, and Teller method surface area measured by nitrogen gas adsorption, which is usually also a linear function of irreversible charge capacity, may be used with certain reservations to calculate approximately the heat evolution of graphitic carbon negative electrode materials in lithium-ion batteries. Graphite materials are usually safer if their irreversible charge capacity during the first cycle is low.