Hybrid Ceramic Solid State Electrolyte for High Performance Solid State Batteries

Abstract

There is a global demand for high energy storage systems for portable consumer devices such as cell phones, laptops, including electric vehicles. Lithium ion batteries (LIBs) are the most promising options due to the high volumetric, gravimetric energy, and power densities. Current LIBs using LiCoO 2 , LiNiO 2 , LiMnO 4 , and LiFePO 4 cathodes coupled with a graphite anode exhibit a power density of 100-260 Whkg -1 [1]. With the advent of high capacity Li – S system, efforts are focused on replacing low capacity carbon based anodes with Li metal and composite systems. However, the Li metal plating process on Cu/Li substrates shows undesirable performance due to unstable Li plating leading to formation of high surface area Li, loss of Li due to uneven plating/deplating, increase in internal resistance and formation of the deleterious Li dendrites [2-4]. These characteristic plating phenomena, result in low columbic efficiencies, increase in plating/deplating potentials as well as ensuing hysteresis losses. As a result, there is rapid fade in specific capacity/energy density combined with thermal run away due to either increased internal resistance or internal short-circuiting of the cell due to the formation and growth of unwanted dendrites running the risk of explosive failure of the cells. Novel hybrid ceramic electrolytes (HCE) were developed utilizing Inorganic Framework Materials Networks (IFM) with enhanced Li + diffusion utilizing the low activation energy for surface migration. The crystallographic channels in the inorganic framework provide pathways for efficient transport of Li + ions thus making them attractive ceramic electrolyte materials. The ionic conductivity measurements of these ceramic electrolytes were conducted in Li/Li symmetric CR2025 coin cell. These novel ceramic electrolytes show a Li + conductivity of ~ 1.26 x 10 -4 S/cm. Subsequently the coin cells were cycled at different current densities ranging from 0.5mA/cm 2 to 4mA/cm 2 and their plating/deplating over-potentials were recorded and analyzed. These hybrid ceramic electrolytes show low plating/deplating potentials ranging from 100mV@1mA/cm 2 – 450mV @4mA/cm 2 comparable with garnet based solid state electrolytes. Subsequently, the electrolytes were tested for electrochemical performance against Cu and new high interfacial energy alloy based collect collectors identified in a coin cell and their coulombic efficiency recorded. The hybrid ceramic electrolytes show columbic efficiency of ~97-99% for a constant plating and deplating current density of 0.5mA/cm 2 for 1h (charge density~0.5mAh/cm 2 ) when tested with Cu electrodes. The full cell electrochemical performance, SEM analysis of plated and deplated electrodes, combined with Raman and infrared spectroscopy results will be presented and discussed. Figure 1