Dynamics and Structure in Complex Disordered FIC Electolytes: Is There a Maximum Ionic Conductivity in the Solid State?

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9972466MartinThis project will develop fundamental new understandings of charge transport in disordered electrolytes. The ever increasing dependence upon and the performance requirements of electrochemically-based portable energy sources, such as batteries and fuel cells, will rapidly outpace the current technological benchmarks being set by the core technologies of these devices. Battery and fuel cell electrolytes, for example, will have to increase their ionic conductivity by more than a couple of orders of magnitude to keep pace with the ever increasing drain rates required of these devices. That such increases in the ionic conductivities of the solid electrolytes in batteries and fuel cells are possible was not questioned a few years ago. New research by the PI has shown that such may not the be the case. His work on chemically optimized fast ion conducting (FIC) glasses has shown that a strong non-Arrhenius temperature dependence of the ionic conductivity limits the ionic conductivity to values 100 to 1000 times below that expected. This phenomenon will have tremendous design implications for the multitude of electrochemical-energy based devices that are on the marketplace today and whose numbers are growing at an exponential rate. In this project, the conductivity of new silver-ion conductors will be measured to higher temperatures and wider frequency ranges to determine if the conductivity reaches a saturating or maximum value. Then, new lithium-ion conductors will be measured to see if the non-Arrhenius conductivity is universal. Wide frequency range nuclear spin lattice relaxation rate (NSLR) and conductivity measurements will be combined to determine if a temperature independent distribution of activation energies can be used to fit the temperature and frequency dependence of both the NSLR and the conductivity. Such fitting will be a powerful test of whether simple activated process theory describes the ion dynamics or whether additional dynamical effects must be included. In addition, theoretical models of the temperature and frequency dependence of the conductivity that include strong many-body interactions will be developed, inelastic neutron scattering and high frequency conductivity studies of the full time-domain response from the strongly interacting regime into the short time weakly interacting regime will be performed, molecular dynamics simulations of the atomic-level conduction topologies will be developed, and elastic neutron scattering studies will be performed to probe glass structure at the intermediate range level where site connectivity is important. The project will involve graduate student research teams working with undergraduate and high school students in a strong collaboration with both US and international researchers as well as a domestic battery manufacturer. %%%The ever increasing dependence upon and the performance requirements of electrochemically-based portable energy sources, such as batteries and fuel cells, used in so many consumer products, demand better and better energy sources. This project will provide understanding of the relationships between the chemistry of the electrolyte and its performance and thus will enable design at the nano-scale of new electrolytes with order of magnitude increases in ionic conductivities. The strong research team the PI has built, along with the international collaborations, promise advances in this area.***