The use of lithium metal as a negative electrode in a lithium-ion rechargeable battery can increase its energy density, but so far, its use is limited due to uncontrolled and inhomogeneous electrodeposition on cycling the battery due to rapid battery fade and safety issues. To solve the Li metal problem and prevent battery degradation in batteries more generally, we must understand both how the electrolyte – the liquid that transports the ions in a battery from the anode to cathode and vice versa – and the passivation layers that protect both the anode and cathode function and fail. Clearly this work is important because the development of better batteries underpin European and Global goals to reduce CO2 emissions. We must develop more sustainable batteries that last longer before failing and have higher energy densities (i.e. can run longer on a single charge).
An important tool to improve battery technology is nuclear magnetic resonance (NMR) spectroscopy because it allows chemical species to be identified. We have been pushing the use of operando methods to do this so as to understand how the different components of the battery operate synergistically. A challenge however with this method is its low sensitivity. This means it is difficult to pick up minor components – be in the molecules formed during degradation or at the interfaces in and between the various layers that make up the battery. We have thus been developing new methods to enhance the NMR signals and have applied them to look at battery reactions and Li metal dendrite formation. The overall objectives are to develop new NMR metrologies specifically designed to target key reactions or species in batteries and then to apply them to understand function and provide insight into how improve battery performance.
