Investigating the batteries of tomorrow for efficient energy storage

Batteries underpin huge swathes of modern life, but they come at a cost. Current technology is limited in its performance by the employed materials, relies on increasingly dwindling rare earth metal resources and can, in the rare case of a mechanical failure and resulting combustion, pose harm.

Finding alternatives to traditional batteries is a prolific research area, and scientists at the Institut Laue-Langevin (ILL) have been investigating new materials set to level up the global battery infrastructure. 

Over the last decade, interest in materials known as superionic conductors has been growing, with an explosion in the amount of cutting-edge research in the hunt for high performance materials for batteries. In a recent study from ILL, two principal materials Li3YCl6 and Li3YBr6 were investigated, as they had shown promise in previous studies as being high performance and of good electrochemical stability, making them ideal candidates for use in cathode composites or as separators on the anode-side in batteries. While the materials themselves are already promising, research has shown that the elements in these compounds can be substituted, improving their electrochemical performance even further. This also allows scientists to explore ways to improve stability and performance by precisely modifying these properties. 

Whilst the two materials studied may seem very similar, only differing in the presence of one anion, the study demonstrated that their properties and structures are vastly different. By exchanging the elements within a compound, researchers could determine which iterations provide the best ionic transfer with the fewest drawbacks. 

These materials are not yet being used commercially, but research into these compounds is fundamental for realising their potential, and greater understanding of their electrochemical properties is needed to unlock safer batteries for tomorrow. The knowledge gained from this research lays the foundation for future breakthroughs, as analysis of the properties and structure of lithium compounds enables informed decisions to be made regarding the most sustainable, cost effective or reliable compositions for batteries. These studies will help to uncover the optimal structure and compound variations that will maximise output, whilst minimising the relative density of expensive-to-mine rare earth metals. 

Neutron diffraction techniques at ILL are perfect for analysing materials with light elements such as lithium, which do not have the density of electrons in their atoms, to be picked up by X-ray diffraction. This is combined with a highly detailed picture of atomic crystalline structures in this inorganic compound enabled with neutron scattering. 

Previously proposed crystalline structures of these materials were overthrown by the findings at ILL, as were previously accepted scientific propositions about how the performance of these materials could be enhanced. It had also been proposed that these types of materials might be less susceptible to degradation in water, but this was not backed by the experiments conducted. 

Investigation into the materials of the future is one of the main uses of the ILL facility, with the most powerful neutron flux in the world and advanced measuring instruments making it an unparalleled location for this type of experiment. Developing batteries of the future, to lower energy costs and develop sustainable solutions to our climate challenges, cannot be done without rigorous scientific analysis. More accurate descriptions of crystallographic structures in this way provides a reliable characterisation of materials we can use for new innovations in batteries.

The neutron experiments were performed on the D2B high resolution powder diffractometer at the ILL.

Re.: ‘Insights into the Lithium Sub-structure of Superionic Conductors Li3YCl6 and Li3YBr6’ Chemistry of Materials (2021). 
DOI: 10.1021/acs.chemmater.0c04352