Polymeric backbone eutectogel electrolyte: Preparation of a composite positive electrode for high-energy density lithium-ion batteries

The need for sustainable mobility leads to a growth of the market of electric cars. At this moment, lithium-ion batteries (LIBs) are the most suitable technology due to their high gravimetric and volumetric energy density. In all roadmaps for battery development, solid-state batteries are the next step after advanced LIBs. They offer the potential to significantly increase the energy density, combined with a higher safety due to the absence of a flammable liquid electrolyte. During the last years, research on solid state batteries has significantly increased, but still faces many challenges, such as the development of a high performant solid electrolyte, the integration of the cathode active material with the solid electrolyte, and the integration of the lithium metal anode with is needed to obtain the predefined energy densities.

In polymeric eutectogel (P-ETG) hybrid solid-state electrolytes, a deep eutectic solvent (DES) is enclosed within a polymer host. They are promising for application in high-energy LIBs due to their relatively high ionic conductivity at room temperature, their improved safety compared to conventional electrolytes, and their compatibility with high-potential positive electrode materials. Further, they can be obtained through a facile synthesis method, i.e. by UV-curing. However, the development of solid-state batteries is not only limited to the development of new solid electrolytes. The replacement of the conventional liquid electrolyte by solid electrolytes introduces new challenges for cell production processes. For commercial application of solid electrolytes, a wet/solution-based process is preferable. Here, we report the preparation of a composite positive electrode for high-energy density LIBs by infiltrating the P-ETG electrolyte precursor solution into the pores of the positive electrode. LTO | NMC622 cells using infiltrated NMC622 positive electrode result in an improved discharge capacity and capacity retention compared to the non-infiltrated NMC622 positive electrodes.