The use of liquid organic electrolytes in lithium ion batteries causes serious safety concerns due to the high flammability, thermal instability, and low cyclability of the electrolytes. In response to these concerns, solid-state lithium-ion electrolytes are being investigated as replacements. The solid-state electrolytes are compatible with a lithium metal anode, allowing for large capacity, but require cathode optimization. Electrochemical half cells were created in the CR2025 configuration with lithium metal as the reference electrode. A solid-state lithium-rich antiperovskite electrolyte membrane (200-400μm) was synthesized by casting lithium salts. The testing has since shifted from carbon coated copper to cathode materials including metal oxides and commercially available cathodes. Impedance spectroscopy was used to measure the ionic resistance and conductivity through the electrolyte membranes from 10mHz–200kHz. The ionic resistance of the electrolyte had a minimum of 4 kΩ at 100oC. This correlates to a peak ionic conductivity of 10-2.3 S/cm and activation energy of 0.23 eV at 100oC. Lithiation and delithiation of the membrane was detected by cyclic voltammetry in the range of 0.05–1.00 V when testing at a rate of 0.1 mV/s. The phenomena was only detected in the elevated temperature range of 50–100oC. Cathode materials will be studied at higher potential ranges. Reversible charge and discharge of the half-cell was measured using rate capability. The cell was tested at C/20–C/10–C/5–C/20 rates at 50-100oC in the voltage range of 0.05–1.00 V. Reversible charge and discharge was observed at elevated temperatures. Cyclability of the half-cell measured at 100oC showed approximately 75% capacity retention over 700 cycles at C/5 rate. Five commercial cathode materials were chosen for impedance, rate capability, and cyclic voltammetry tests later used for evaluation of their chemical compatibility and electrochemical stability in contact with the solid-state electrolyte in lithium-ion full cells with lithium metal as anode. By integrating cathode material with this solid-state electrolyte, it is possible to achieve similar capacity to liquid lithium-ion batteries. This would maintain the performance of typical lithium ion batteries at a fraction of the weight while increasing the thermal stability and cyclability of the battery. Once optimized, solid-state lithium-ion batteries are expected to replace liquid lithium-ion battery cells.

Integration of lithium-rich, anti-perovskite electrolyte with cathode material

2019 Spring National Meeting

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