This study deals with the electrochemical properties of fly ash collected by electrostatic precipitators at fossil-fuel power planls. The collected samples, called EP-ash, consist mainly of carbon with a microporous spherical morphology. The EP-ash electrodes show lithium insertion-extraction ability with some irreversible capacity. A simple washing treatment improves the electrochemical properties. The EP-ash can be charged and discharged successfully beyond 100 cycles with a reversible capacity above 200 mA h g(-1), even though it contains many contaminants.