This research presents a groundbreaking unification of two traditionally distinct energy storage mechanisms: insertion and supercapacitive storage. By investigating titanium oxide thin films of varying thicknesses, the study reveals that these processes can coexist and influence each other. The key to understanding this phenomenon lies in the energy landscape of charge carriers within the material and its interface with the current collector. The relative dominance of insertion or supercapacitive storage depends on factors such as film thickness, electronic conductivity, and the energy levels of the charge carriers. Thicker films and higher electronic conductivity favor insertion, while thinner films and easier charge accommodation in the current collector promote supercapacitive storage. This unified approach offers a powerful tool for tailoring energy storage devices. By strategically manipulating material properties, researchers can optimize power density and energy density, addressing a critical challenge in energy research. This work not only provides a fundamental understanding of energy storage mechanisms but also paves the way for the development of advanced energy storage solutions. Corroboration for the unified storage model is obtained by advanced atomic-resolution scanning transmission electron microscopy in combination with electron energy-loss spectroscopy.

Details can be found at C. Xiao, H. Wang, R. Usiskin, P. A. van Aken and J Maier. Unification of insertion and supercapacitive storage concepts: Storage profiles in titania. Science 2024, 386(6720), 407. https://www.science.org/doi/10.1126/science.adi5700.