Advanced lithium-sulphur batteries with potential to deliver high energy
Compared to the common lithium-ion battery, lithium-sulphur batteries have important advantages. Sulphur is lightweight and abundant, with a high energy capacity and high depth of discharge. However, existing lithium-sulphur battery technology suffers from the low electrical conductivity of the cathode and the irreversible loss of active materials when dissolving lithium-sulphur into the electrolyte. In the EU-funded project EUROLIS (Advanced European lithium sulphur cells for automotive applications), scientists introduced new developments to tackle these shortcomings. The team used polysulphide reservoirs with modified surfaces to stabilise lithium-sulphur cathodes. The proposed system with a high surface area enables weak adsorption of polysulphide intermediates and also reversible desorption. The active material is therefore fully utilised. To further understand the impact of the surface area and the interactions between electrolyte and sulphur-based cathode composites, reliable characterisation techniques are required. EUROLIS developed a number of different in situ and ex situ tools for analysing lithium-sulphur batteries at different stages of discharge and charge. This helped further understand the electrochemical properties of the lithium-sulphur battery. EUROLIS used these to effectively monitor polysulphide formation and diffusion or migration in different parts of the lithium-sulphur battery. Scientists successfully investigated a range of different carbon materials for use as sulphur’s host structures. Focus was placed on how the carbon material shape affects the battery’s electrochemical performance, how chemical composition affects capacity fading, and lastly on the development of large-scale synthesis routes. Project work led to the development of three generations of lithium-sulphur battery prototypes. Separators, lithium and electrolyte filling were adapted to prepare 12 prototype cells in a standard configuration. Scientists also benchmarked alternative lithium-sulphur technologies: the combination of lithiated silicon in the anode and sulphur in the cathode, performance testing of a flow battery using catholyte, and finally, the development a solid-state sulphur battery based on a ceramic separator. EUROLIS offered practical solutions to the chemical challenges inherent in lithium-sulphur batteries. With high energy density and relatively low cost, lithium-sulphur batteries offer great promise for electric vehicles, helping take them on longer drives before needing to charge.
Keywords
Lithium-sulphur batteries, energy density, electric vehicles, EUROLIS, polysulphide
