Quantum Chemical Investigation of Thermotropic Ionic Liquid Crystals to Predict Phase Transition Temperatures

With the rising need for high capacity and efficient energy storage for renewable energy sources and electric vehicles, developing high-capacity lithium metal batteries (LMBs) has gained renewed attention. Dendrites growing from uneven electrodeposition of lithium ions cause battery malfunction and fire hazards, thus being the biggest obstacle for LMBs. Liquid crystal is a phase, also called mesophase, between crystal and liquid. Thermotropic liquid crystals exhibit multiple phases including one or more mesophases, depending on temperature. Ionic liquid crystals consist of two charged compounds, usually one large molecule and an ion coupled to it, which provides ion conductivity. Thermotropic ionic liquid crystals (TILCs) combine both into a versatile material with properties of both. The application of TILCs as dendrite-inhibiting, self-healing electrolyte (SHE) for LMBs is discussed. In the computational part of the thesis, the Results from DFT calculations of 10 TILCs and 11 non-ionic thermotropic liquid crystals are presented. Correlation between experimental liquid–liquid crystal phase transitions with various quantities obtained through DFT are investigated. A strong correlation is found for zero point vibrational energy and transition temperatures are predicted for additional molecules. Recommendations for TILCs with lower transition temperatures than those of the source material are presented. Further methods, such as multivariate regression and machine learning (ML) are recommended for a more reliable model. An automated computational workflow model for high-throughput DFT calculations using TURBOMOLE is presented.