The portable electronics boom has been driven by advances made in Li ion battery technology, following the initial work on the lithium cobalt oxide cathode material by Goodenough and co-workers. Other notable advances in terms of phosphate containing cathodes have extended the applications of lithium ion batteries to higher charge/discharge rate applications such as power tools and transport. Applications in terms of the latter have intensified the already substantial interest in lithium ion batteries, as a result of the environmental benefits of hybrid and all electric cars. Further applications as energy storage for renewable sources have also been proposed to overcome the intermittency of supply problems of renewable energy sources such as solar or wind power. While research on new lithium ion battery electrode materials has been intensive, the development of new electrolyte materials has received comparatively less attention.
In a typical Li ion battery, the electrolyte is usually a Li salt in an organic solvent, as a result of the high Li ion conductivity of such systems. The flammable, toxic and volatile nature of such electrolytes, the instability in conjunction with higher voltage electrode materials, and the desire for miniaturisation are placing distinct limitations on further advances with conventional liquid electrolyte batteries. The use of a solid state electrolyte allows the potential to overcome these problems along with supplying a range of other advances including the simplified production of high voltage battery packs. A further unique advantage of solid state batteries is their low leakage currents, which delivers other potential applications in terms of use in energy harvesting devices. Furthermore the desire for shape-flexible, wearable electronic devices offers another avenue for the exploitation of all solid state battery systems.
This interdisciplinary project involving researchers from chemistry, materials science, chemical engineering and industry aims therefore to develop new Solid State Li ion batteries. Such all solid state cells have been identified as one of the most important future targets in battery research, as illustrated by their inclusion as one of the fast-track projects in the Faraday challenge (industry strategy challenge objective 2). The importance of these batteries lies in their potential to deliver improved safety, reduced size, and higher capacity, as well as to open up new applications such as energy harvesting devices. In particular, the demonstration of a commercially viable scaleable ceramic-based electrolyte with higher safety will offer large benefits in terms of UK wealth generation/investment opportunities (Industry strategy challenge objective 1). In terms of potential commercialisation, the optimisation of garnet Li ion conducting electrolytes, their scale-up synthesis and demonstration in all solid state batteries offers significant potential in terms of Li ion battery technology, with applications ranging from portable consumer devices to transport. In terms of helping to ensure the delivery of impact in this area, a strong link has already been set up with industry, to provide key input into the project from an industrial viewpoint, along with industrial validation of the full cell tests on the most promising systems (industrial strategy challenge objective 3). This will allow UK industry to capitalise on the developments made during this work and offer an early route to exploitation (Industry strategy challenge objective 1).

Potential Impact:
Lithium Ion batteries have revolutionised our daily life, with their development leading to the portable electronics boom. More recently they have found use in further applications in terms of hybrid and all electric vehicles. The key benefits of Li ion batteries for such applications are their high power and light weight. However, there are still a number of issues concerning these batteries, with the current electrolyte materials having significant limitations. In particular, these liquid electrolytes tend to be flammable, and unstable in contact with higher voltage electrodes. In addition, the need to contain the liquid electrolyte leads to individual batteries and battery stacks that are larger than ideal. This project is aimed at the development of a suitable solid state electrolyte to overcome such issues, and offer other avenues for further applications, such as energy harvesting devices and shape-flexible, wearable electronic devices. The development and scale up of such solid state electrolytes, and batteries utilising them, will therefore further enhance the applications of Li ion batteries: in particular in terms of transport applications, such advances in battery technology will lead to cleaner transport, thus reducing greenhouse gas emission levels, and so helping the UK to fulfil targets set by the Climate Change Act to cut its emissions by at least 80% from 1990 levels by 2050. The improved safety of such solid state electrolytes will also help ensure that issues regarding flammability, such as the recent Dreamliner battery fires, become a thing of the past. Furthermore, the low leakage rates and potential for miniaturisation of such batteries will open up new avenues for these battery systems as noted above, leading to further significant commercial benefits.