Beyond the age of oxides; new materials for safe and sustainable solid-state batteries.

"ecent safety issues in applications from cell phones to airliners highlight the potential hazards associated with liquid electrolytes in high voltage Li-ion batteries. Such dangers could be avoided if a solid electrolyte alternative could be found that combined stability (both chemical and thermal) with high Li-ion conductivity and a wide potential operating window. Halides and hydrides are extremely attractive contenders for this role, with the unique feature that the non-oxide anions can promote the transport of Li-cations synergically. Moreover, their outstanding (electro)chemical stability paves the way for cells in excess of 5V and the use of novel, higher activity anodes, such as electrides.
This project involves the design of new materials containing non-oxide polyanions (e.g. borohydride, boranes, complex halides) in which rotating/"tumbling" anions interact symbiotically with the highly mobile cations within prescribed Li-ion diffusion pathways. Our ambition is to exploit these interactions (modelled by both experiment and theory) to control the mobility of the Li-ions as a function of the polarisability and density of the anion sublattice (determining all aspects of the free movement of the Li-ions). These concepts will then be translated to novel solid state battery chemistries in which Li+ is replaced by Na+ or Mg2+ as the mobile cation. The aim of this approach is to migrate to more sustainable battery architectures based on cheaper, more Earth-abundant metals, without sacrificing performance. All new materials will be synthesised by sustainable, energy-efficient methods before being characterised and tested in rechargeable cells. "