Aging Mechanisms and Calendar-Life Predictions in Lithium-Ion Batteries

Conclusion

Providing a good choice of active materials Li-ion systems can exhibit excellent cycling and calendar life. The main identified aging parameters include:

• 1. Negative electrode SEI slow growth, resulting in lithium loss, associated with some impedance increase. Capacity loss can be modeled through a parabolic equation of corrosion in time following an Arrhenius law with temperature, and not depending on SOC.

• 2. Electrolyte oxidation on the positive electrode, producing an impedance increase, probably due to carbonate polymerization at the interface. This effect depends strongly on SOC, temperature, and surface reactivity. The interfacial chemistry, influenced by impurities, plays prominent role.

A very positive point is that the identified aging mechanism follows only monotonous evolution, which minimizes risks of sudden failures, and allows extrapolations with some good probabilities of success.

Although many phenomena still remain to be clarified in more detail, and because the lithium-ion system is still a relatively new electrochemical system, the first experiments over extended period of time are very promising. Many applications, where longevity and reliability are of most importance can now benefit of the high energy and power density of these systems.