Stress evolution of thin film RuO₂ Li-ion battery electrodes

Abstract

Abstract Thin Film Li-ion batteries (TFB) are seen as a promising candidate for powering small, low power microelectronic devices as they exhibit high energy density and can operate reliably at low voltages. Currently the biggest obstacle to TFB battery development is high volume expansion and material degradation in electrodes with high theoretical Li ion capacities. Among these materials is RuO₂, which exhibits excellent capacity and great potential for use as either cathode or anode in low power electronics. In order to better understand the mechanisms that underlie mechanical failure in RuO₂, we perform the first in situ measurement of mechanical stress evolution in thin film RuO₂ electrodes. The results of these measurement reveal a very unique stress evolution pattern in RuO₂, which has not been observed or modeled in any previous experiment, exhibiting near zero stress delithiation and linear increase in stress during lithiation. These results point to a mode of failure of RuO₂ which does not occur in other materials currently being studied.