Effects of Irradiation Induced Defects on TiO2 Electrodes for Lithium Ion Batteries

Abstract

We are living in a time of growing concerns over population growth, energy consumption, and climate change. These issues are driving the need for advanced electrochemical energy storage (EES) technologies, such as batteries, to support a shift to renewable energy sources. After their commercialization in the 1990’s LIBs have dominated the field of portable electronics, and have become one of the most promising EES systems for renewable energy systems. Even so, the future demands of EES technology will require LIBs to offer increased energy and power density, improved safety, and longer cycle life. As such, recent studies have investigated enhanced electrochemical charge storage in electrodes that contain intentional structural defects. A new approach to introduce defects in electrode materials is to use ion irradiation to produce damage cascades which result in point defects in the target material. The objective of this work is to investigate the fundamental effects of irradiation on nanostructured TiO2, and to understand how these effects can alter the electrochemical charge behavior when the oxide is used as an electrode in Li-ion batteries. Our work suggests that tailoring the defect generation through ion irradiation within metal oxide electrodes could present a new avenue for design of advanced electrode materials. In this study, we first focus on separating the effects of irradiating species on defect production by conducting proton, niobium, and nickel irradiations on [100] and [110] rutile TiO2 single crystals. We then extend our study to nanostructured TiO2, irradiated with protons. After room temperature irradiation the nanotubes undergo an irradiation-induced phase transformation accompanied by a 35% reduction in capacity compared to anatase TiO2. On the other hand, proton irradiation at 250 °C induced a disordered rutile phase which along with a 20% increase in capacity. Voltammetric sweep data was used to determine the contributions from diffusion-limited intercalation and capacitive processes and it was found that the electrodes after irradiation has more contributions from diffusion in lithium charge storage. Our work suggests that tailoring the defect generation through ion irradiation within metal oxide electrodes could present a new avenue for design of advanced electrode materials. Figure 1