Design of High Voltage All-Solid-State Batteries Based on Sulfide Electrolytes

Abstract

Ceramic sulfide solid-electrolytes are amongst the most promising materials for enabling solid-state lithium ion batteries. With ionic conductivities that can meet or exceed liquid-electrolytes, such ceramic sulfides are limited in practice chiefly by a narrow electrochemical stability window of approximately 1.7-2.1 V vs Lithium metal. In addition, ceramic sulfides are frequently plagued by interfacial reactions when combined with common electrode active materials. In this talk, methods for the stabilization of both the bulk electrochemical decompositions and the interfacial reactions will be discussed. Solid-state cells stable up to 5V, including layered Li-Co-O and spinel Li-Mn-Ni-O, will be presented and the stabilization mechanisms will be discussed from a detailed theoretical perspective. Ceramic sulfides are known substantially swell during electrochemical decay. Such swelling has been shown to provide a viable means by which to stabilize electrochemical decomposition in lithium ion batteries[1]. Evidence and theoretical understanding of stability window expansion as the result of mechanical constriction will be discussed for both Li10GeP2S12 and Li10SiP2S12 systems. Further discussion on the impact of interfaces will focus on our novel high-throughput computational schema[2], which has enabled the evaluation of nearly 70,000 material DFT calculation for interfacial stability with Li10SiP2S12. These new computational methods found over 2,000 high-voltage coating materials that are electrochemically inert against Li10SiP2S12 at standard cathode voltages. The culmination of these approaches, mechanical bulk stabilization combined with interfacial coating layers, is the design of solid-state full cells with high voltage stability and good cyclability. The principal focus of this talk will be a discussion on the theoretical underpinnings of these methods and a comparison with experimental data. [1] Fan Wu*, William Fitzhugh*, Luhan Ye, Jiaxin Ning, Xin Li. Advanced Sulfide Solid Electrolyte by Core-Shell Structural Design. Nature Communications, (9), 4037 (2018). [2] William Fitzhugh*, Fan Wu*, Wenye Deng, Pengfei Qi, Luhan Ye, Xin Li. A High-Throughput Search for Functionally Stable Interfaces in Sulfide Solid-State Lithium Ion Conductors. Advanced Energy Materials. Under review.