Mixed Conducting Electrodes for High Energy Lithium-O2 Batteries

The overall objective of this proposal is to pursue an effective and target driven leap forward with high-energy Li-O2 batteries based on the concept of mixed ion and electron conductors. Electrification of transport is essential for reducing greenhouse gas emissions. Existing battery technology offers too low energy density at too high cost for this purpose. New battery materials that allow for a leap in cost and energy density against current lithium-ion batteries have in common poor conductivity and/or high volume changes upon electrochemical cycling. State-of-the-art carriers for ions and electrons fall short in addressing this problem. The optimum solution can be anticipated to be a mixed ion and electron conductor that follows volume changes and provides at any stage intimate contact with electrons and ions. The project therefore directly tackles fundamental challenges of this potentially transformative battery rather than seeking stepwise improvements with existing approaches. Preliminary results show that the concept is feasible and offers unprecedented opportunities. With this approach electrodes can be envisioned that adapt their thickness to the state of charge. This allows maximizing the energy density of the cell by avoiding dead volume and mass. We develop and combine advanced synthetic, electroanalytical and spectroscopic methods to realize the concept. The proposed project has high chances to make a significant advance with the Li-O2 battery by making a rational approach onto the fundamental causes that hamper functioning so far. It tackles fundamental issues of charge transport in this battery rather than seeking incremental improvements of existing approaches. This innovation can unlock the outstanding potential of the high energy Li-O2 battery. The time is right to start this research now as there is tremendous worldwide upsurge in activities to find solutions for this target. The grand target of this project is to establish this new direction in this field, to demonstrate its potential and make progress in the underlying fundamental science. The achievement of this target can open the door to game-changing electrochemical energy storage. I have all necessary skills to establish this new line of research.

The battery market demands major improvements of batteries in several directions including the energy stored per mass and volume, the cost and the environmental impact and recyclability. Current concepts of Li-Ion batteries relying on Li-insertion materials cannot meet these requirements in combination. Therefore so called conversion type materials are pursued that promise to make a step change with either of these requirements. However, the involved storage materials have in common poor conductivity and high volume changes, which make it more difficult to make working batteries with these materials. One of these materials is lithium peroxide (Li2O2), the active material in the Li-O2 cathode, which exhibits the highest known theoretical energy density. State-of-the-art carriers for ions and electrons fall short in addressing this problem. The optimum solution can be anticipated to be a mixed ion and electron conductor that follows volume changes and provides at any stage intimate contact with electrons and ions. The objective of this project is to pursue a leap forward with high-energy LiO2 batteries with the concept of mixed ion and electron conductors. In the first months of the project we developed the building blocks of the mixed conductors and methods to investigate the mechanism of the cycling reaction and possible sidereactions. Both of which are required to fully exploit the outstanding potential energy density and to make the batteries last for many cycles. After 7 months the project was continued in the ERC Starting Grant project of the project leader.