Study of Phase Change by Transmission Electron Microscopy
Ni, Yizhou 1991-
MetadataShow full item record
Fossil fuels such as gas and petroleum account for more than 80% of energy sources, but these natural energy sources are approaching depletion. Renewable energy such as solar energy and high-performance electrical energy storage technology including batteries are considered as alternatives for fossil fuels, as they provide more clean, efficient and uninterruptible power supply in comparison to the fuel. Among these two technologies, phase change material plays a significant role. Different phase of TiO2 nanotubes have various applications in energy storage, so the mechanism of the physical phase change process of TiO2 nanotubes and their stability at each phase (anatase, brookite, and rutile) gained a lot of attention and have been widely studied. For battery technologies, energy stores into electrode materials when they have chemical phase change during charge and release when they undergo a reverse chemical phase change during discharge. Hence, the research into the chemical phase change process of batteries will contribute to the enhancement of cycling performance. Here, in situ heating TEM technology was used to study the phase change process of TiO2 nanotubes over different temperatures, finding that anatase, brookite, and rutile phase would appear with the temperature ramp and finally collapse at the temperature over 1200 ℃. Different phase change processes were also observed with nanotubes of various wall thickness, which can be attributed to different surface energies of TiO2 of diverse size. Ex situ/in situ TEM observations were executed to the charging/discharging processes of lithium-ion battery with porous-Si nanorods@void@nitrogen-doped carbon as anode material and sodium-ion battery with Black K2Ti6O13 nanowires as anode material, explaining how the anode materials with nanostructures can achieve high cycling performance.