Insights in the interaction between the eutectogel solid electrolyte and cathode active material

Abstract

The need for sustainable mobility leads to a growth of the market of electric cars. At this moment, lithium ion batteries are the most suitable technology due to its high gravimetric and volumetric energy density. In all roadmaps for battery development, solid state batteries are the next step after advanced Li-ion batteries. They offer the potential to significantly increase the energy density, combined with a potentially 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 fundamental challenges, such as the development of a high performance solid electrolyte, integration of the cathode active material with the solid electrolyte, and the integration of the Li metal anode which is needed to obtain the predefined energy densities. In this study a polymer based eutectogel is used as the solid electrolyte. The eutectogel is a new class of solid composite electrolytes in which a deep eutectic solvent (NMAC/LiTFSI) is confined within a polymer matrix. Such an electrolyte allows the combination of the processability advantage of polymers with the high Li-ion conductivity of liquid electrolytes, thus overcoming the primary disadvantage of solid polymer electrolytes. The aim of this study is to obtain insights and expertise in the interaction between this type of eutectogel electrolyte and the cathode active material. Preliminary coin cells with the eutectogel solid electrolyte and NMC cathode material were assembled, showing promising results. To understand performance limiting factors at the interfaces (cathode-eutectogel, eutectogel-anode), electrochemical studies have been performed using tools such as: galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy.