title: Memory effect in a lithium-ion battery.
abstract: Memory effects are well known to users of nickel-cadmium and nickel-metal-hydride batteries. If these batteries are recharged repeatedly after being only partially discharged, they gradually lose usable capacity owing to a reduced working voltage. Lithium-ion batteries, in contrast, are considered to have no memory effect. Here we report a memory effect in LiFePO4-one of the materials used for the positive electrode in Li-ion batteries-that appears already after only one cycle of partial charge and discharge. We characterize this memory effect of LiFePO4 and explain its connection to the particle-by-particle charge/discharge model. This effect is important for most battery uses, as the slight voltage change it causes can lead to substantial miscalculations in estimating the state of charge of batteries.
authors.affiliation: Electrochemistry Laboratory, Paul Scherrer Institut, Villigen PSI, Switzerland. sasakit@mosk.tytlabs.co.jp
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Sasaki
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Ukyo
authors.forename: Petr
authors.initials: P
authors.lastname: Novák