There is more at stake in battery development than longer-lasting AAs. In order for electric vehicles to compete with conventional models, car batteries must be cheaper, i.e. more efficient: "If the batteries could store more energy, automakers could use fewer of them, thus saving money. In conventional lithium-ion-battery manufacturing, electrode materials are applied in the form of slurry to metal foils. The thickness of the electrode is limited by the rate at which lithium ions can diffuse out of the material to reach an electrolyte."