UC San Diego

Current state of the art commercial lithium ion batteries (LIB) have been successful power sources for portable electronics. The success of this battery has led to its penetration into electric vehicle and grid-scale storage markets. However, large quantities of LIB batteries pose a threat to public safety, as they are capable of explosive results due to the flammability of the electrolyte.

All-solid-state battery (ASSB) technology is gaining attention because it has properties that can address all the shortcomings of LIB, such as: improved safe battery operations using non-volatile and non-flammable components, enabling the Li metal anode, preventing dendrite propagation, high voltage operation, suitable mechanical properties, and high transference number. Among the known solid electrolytes, sulfides have shown promise due to their processibility at lower temperatures, high ionic conductivity, and ductility compared to their oxide analogs.

Herein, we investigate new SSE material and evaluate their structure and properties. The crystal structure of the SSE is solved through x-ray diffraction. The performance of the SSE is evaluated through electrochemical means such as: electrochemical impedance spectroscopy, Arrhenius behavior, electrochemical stability window, and galvanostatic charge and discharge performance in a battery.

SSE for ASSB is demonstrated to have comparable room temperature ionic conductivity as their LE counterparts. Their performance can be further improved through post-processing reducing grain boundary impedance and defect engineering. The interface of the SSE and electrodes are a formidable technical hurdle to understand and overcome due to their buried nature in the ASSB configuration. The most complex of interface is the cathode/SSE interface where parasitic reaction products are formed by chemical and electrochemical means occurs. Through proper interface engineering, the stability of the interface can be improved.

A lithium metal anode is demonstrated to reversibly cycle with high voltage cathodes and Li-S chemistries shorting and showing a pathway to safe and high energy density ASSB.