Discovery of “Memory Effect” in Li-ion Battery

Until now, lithium-ion batteries have been widely believed to exhibit no memory effects. However, we hereby report the first ever observation of a memory effect in a lithium-ion battery. The figure shows that a small bump appears in the voltage vs. SOC *1 curve at an SOC of 50% due to the memory effect, as indicated by the red arrow. The effect is observed at precisely the same point at which the previous partial charging cycle was terminated, as though the battery memorized this SOC value. Although the voltage change due to the memory effect is far smaller than that for Ni-Cd or Ni-MH batteries, it is essential to be able to understand and predict this phenomenon, in order to precisely estimate the SOC, and ensure the safe and effective use of lithium-ion batteries.
This work, carried out in collaboration with The Paul Scherrer Institute was published in the scientific journal Nature Materials in 2013.

• *1 SOC : State of Charge