LSBs are viable candidate for the commercialisation among all post Li-ion battery technologies due to their high theoretical energy density and cost-effectiveness. Despite many efforts, there are still remaining issues that need to be solved and this will provide final direction of lithium sulphur batteries technological development. Some of the technological aspects, like the development of host matrices, interactions of host matrix with polysulphides (PS) and interactions between sulphur and electrolyte have been successfully developed within FP7 project EUROLIS (www.eurolis.eu).Open porosity of the cathode, interactions between host matrices and PS and proper solvatation of PS are requirements for the complete utilisation of sulphur. A possible direction to improve cycling properties is an effective separation between electrodes. Additionally, lithium metal protection and reduction of electrolyte quantity in the final cell configuration are required if we want to meet objectives connected with long life and high energy density.
The HELIS project has been addressing remaining issues connected with a stability of lithium anode during cycling, with the engineering of complete cell and with questions about lithium sulphur batteries cells implementation into commercial products (aging, safety, recycling, battery packs).Instability of lithium metal in most of conventional electrolytes and formation of dendrites due to uneven distribution of lithium upon the deposition cause several difficulties. Safety problems connected with dendrites and low Coulombic efficiency with a constant increase of inner resistance due to electrolyte degradation represent main technological challenges. From this point of view, stabilisation of lithium metal will have an impact on safety issues. The stabilized interface layer is important from the view of engineering of cathode composite and separator porosity since this is an important parameter for electrolyte accommodation and volume expansion adjustment.Finally the mechanism of lithium sulphur batteries aging can determine the practical applicability of LSB in different applications, but the project is aiming towards the development of three different series of Li-S cell prototypes, all of which will be tested according to specifications for automotive use.
The Li-S battery technology in HELIS project is based on low-cost cathode materials. The cost for electrolyte, binder, and separator costs are estimated to be similar to those in the current Li-ion battery technology. The use of a much cheaper cathode will be maintaining low cost of Li-S cells and the final cell price is estimated to be below 150 €/kWh. By achieving 500 Wh/kg energy density this will substantially improve the driving range, thus having a positive impact on EV acceptance.
