Fade in Battery Capacity Schematic (IMAGE) DOE/Brookhaven National Laboratory Caption The fade in battery capacity is due to the formation and thickening of internal and surface passivation layers during charge and discharge cycles. For the electrochemical reactions to occur, lithium ions (Li+) and electrons (e-) must travel through all these layers to reach active nanoparticles (NPs) at the electrode. Top: Fe3O4 (iron oxide) sample after three cycles. Bottom: Fe3O4 sample after 100 cycles. The development of kinetic barriers during long-term cycling limits electrochemical reactions to such an extent that no reduction-oxidation reactions occur at the electrode materials after 100 cycles. Credit Brookhaven National Laboratory Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.