Development of new battery technologies based on alternative Chemistries

Lead Research Organisation: University of St Andrews
Department Name: Chemistry

Abstract

The proposed work will investigate magnesium based chemistries for thermal batteries. The dominance of Li ion research in academia means little work is performed on alternatives to Li; and is especially true for single use high value thermal batteries.
Modern thermal batteries are based on Li13Si4/.../MS2 (M=Fe, Ni, Co). Although these technologies are tried and tested, they are fundamentally limited by their thermal stability.
The anode, Li13Si4 is a problem above 600 degree C and susceptible to thermal runaway. The sulphides show significant dissolution below 600 degree C (esp for FeS2), this can lead to formation of Li2S or free S under certain conditions. These issues limit the temperatures at which thermal batteries can operate, which in turn limits possible applications.
The proposed work will focus on developing stable magnesium based chemistries capable of working at elevated temperatures (time permitting aluminium will be examined).

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N50936X/1 01/10/2015 30/09/2020
1690712 Studentship EP/N50936X/1 01/10/2015 31/03/2019 Stewart Dickson
 
Description The work had sought to explore the possibility of removing lithium from a molten salt battery, which was successfully implemented and analysed in-depth. Both the magnesium and calcium battery systems exhibit interesting new properties not previously seen for these high temperature battery chemistries. Initial results and analysis identify that these routes are promising, as they discharge with either high voltages or capacities at 'low' discharge rates.
However, to achieve a battery which is capable of competing with the high temperature lithium system, more optimisation would be required. For example, the conductivity (i.e. how fast the ions travel through the battery) of the systems is much lower, due to the charge and size of the ions used. Therefore, further study is necessary to improve this and thus create a system which can be discharged much faster. Along with this, further knowledge has been captured to understand how these systems behave, and how they could be modified to achieve a better working prototype. Operando techniques have allowed for the exploration of the system whilst it is at temperature and under electrochemical discharge, which has allowed for much more meaningful results than those achieved from tradition 'ex-situ' analyses. Finally, the work has also exhibited the use of phosphates as potential new cathode materials for thermal batteries. These give higher operating voltages than the tradition FeS2 cathode material, which in turn could afford thermal batteries with improved power capabilities.
Overall, whilst the main aims of the project were met, there was no meeting or improvement of the current lithium battery chemistry, which has likely answered the question of whether multivalent ions could replace it, and could otherwise be used as an alternative in applications which require much lower power batteries if optimised and understood in more depth. Instead, the most important aspect is that this project has begun a much greater study on thermal battery chemistries, such as the use of different materials at the cathode and more in-depth research into other alternatives which could be explored.
Exploitation Route The overall outcomes of this funding could (and are currently) being used by academia and industry to focus the research into thermal batteries in new and interesting directions. It is hoped that publications on the work can also assist other sectors in realising that high temperature batteries can be suitable for new applications.
Sectors Aerospace, Defence and Marine,Construction,Electronics,Energy,Environment,Transport