Hosted by: Ignace Jarrige

Electrochemical energy storage (EES) has become prevalent in daily life for their use in mobile electronics and electric vehicles. More recently, the need for large-scale stationary energy storage to integrate clean and renewable alternative energy sources to the electric grid has arisen. Aqueous EES devices using beyond-lithium charge carriers offer an attractive solution to this problem because of their superior safety, lower cost, and excellent transport properties compared to their organic counterparts. However, improvements in energy density and cyclability are required for implementation. Fundamental research on the charge-storage mechanisms is critical to understanding the structure-function relationship and, thus, for the development of electrodes materials for aqueous EES. Characterization of these electrode materials using synchrotron and neutron techniques provide vital information on the crystalline and electronic structure. Furthermore, time-resolved in situ measurements offer detailed information on structural changes due to the intercalation/de-intercalation of cations and the evolution of the electronic state of metal components during redox reactions. This, coupled with half-cell and full-cell electrochemical measurements, provides valuable insight into the change-storage mechanisms that occur. In this work, advanced characterization techniques have been used to investigate the charge storage mechanisms of nanoscale transition metal oxide electrode materials for aqueous EES. Various types of electrochemical charge storage mechanisms (pseudocapacitive, intercalation, and phase-change) were studied. Numerous strategies for improving the energy density and cyclability have been employed, including; studying the promotional effects of structural water, inducing structural disorder, synthesizing materials with open frameworks, doping with more redox-active components, using multivalent cations as charge carriers, and expanding the available potential window. These results provide a pathway for designing the next generation of aqueous EES devices. ________________________________ Daniel S Charles, Xiaoqiang Shan, SaeWon Kim, Fenghua Guo, and Xiaowei Teng