Sincere: Selective ion-conductive ceramic electrolytes

Li-stuffed garnet electrolytes are poised to provide a breakthrough in battery technology since they can deliver the adequate Li-conductivity and the safety and cycle life required for the commercialisation of high-energy density batteries (i.e. high voltage Li-ion and Li-metal batteries). However, these garnet electrolytes, if they are not processed properly, suffer from severe moisture-sensitivity that leads to drastic degradation of their transport and microstructural properties - a problem that has not been universally recognised in the field. This fast degradation, which occurs even at room temperature, has so far hindered fundamental studies aimed at identifying and optimising the modes of lithium transport within the crystal lattice and the grain boundaries. Furthermore, measurements of the interfacial resistances reflect those of the decomposition products, rather than the intrinsic properties of the garnets themselves. We have developed a unique t setup that will allow a strict control of the moisture during the processing and characterization of the garnets. Our work, to date, has shown a three-fold enhancement in lithium-ion conductivity, if the degradation-related problems are addressed. The aim of this project is threefold: a) Reveal the optimum intrinsic Li-mobility in Li7-nxAxV(n-1)xLa3Zr2O12 (V = lithium vacancy) garnets b) Investigate the electrode/garnet interfaces and c) Analyse the degradation under moisture-controlled conditions to evaluate the potential use of the garnets in Li-air cells.

The development of safe, long life, high energy density secondary batteries is one of the most important challenges in materials science towards safeguarding quality of life for future generations. On the one hand, it will reduce fossil fuel dependency and its associated greenhouse gas emission levels, helping to fulfill targets set by the Climate Change Act for the UK to cut its emissions by at least 80% from 1990 levels by 2050. On the other hand, the successful realisation of such high capacity batteries will allow the production of long-range electric transport requiring mobile storage and release of electrical energy and will support the utilization of green power sources more efficiently for stationary applications. Solid electrolytes such as lithium-conducting garnet ceramic oxides have the potential to provide the breakthrough in battery technology that we seek since they are able to deliver the required safety and stability properties. However, there are some aspects relating to the adequate understanding of Li-conduction paths and degradation processes in these systems that remain unknown, hindering their optimization and integration in commercial batteries. This project represents a unique and timely opportunity to unveil the intrinsic Li conductivity in garnets and to understand and improve the interfacial resistance of the solid electrolyte/electrode interfaces. It will provide invaluable information for optimising the Li-conduction pathways in these materials that will allow the design and production of the best possible ceramic electrolytes to be used in secondary batteries. Furthermore, the project aims to establish a universal procedure for the suitable processing of Li-ceramics that will prevent their degradation and optimise their performance in batteries (i.e. via tuning of the microstructural and electrochemical properties). This will not only have a great impact on the knowledge of these complex and interesting systems but also has potential economic benefits through the introduction of procedures for the commercialization of solid state batteries.