1. College of Engineering and Applied Sciences, Nanjing University, Nanjing 210023, China;2. Shenzhen Research Institute of Nanjing University, Shenzhen 518000, Guangdong Province, China
Abstract:
All-solid-state lithium batteries (ASSB) have emerged as key components in energy storage applications owing to their superior safety characteristics and high energy density. The use of sulfide solid electrolytes has considerably promoted the development of all-solid-state lithium batteries because of advantages such as a high ionic conductivity, formability, and good interface compatibility with electrodes. In this review, we first discuss the issues hindering the use of sulfide-based all-solid-state lithium batteries, focusing on aspects related to the cathode/electrolyte interface, sulfide solid electrolytes, and the anode/electrolyte interface. At the cathode/electrolyte interface, interfacial side reactions inherently occur due to the narrow electrochemical window of sulfide electrolytes when used with high-voltage cathode materials, which degrades the battery performance. In addition, owing to the chemical potential difference between cathode materials and sulfide solid electrolytes, the space-charge layer generated due to the formation of a lithium depletion layer is also detrimental to the cell performance. To overcome these difficulties, inert coatings, replacing sulfide solid electrolytes with halide solid electrolytes, and replacing frequently used transitional metal oxide cathode materials with other materials that are better suited for sulfide solid electrolytes to modify the composite cathode have been explored. Improvements in the ionic conductivity and air stability are imperative for sulfide solid electrolytes. Strategies to optimize the solid electrolyte have mainly focused on doping or adjusting the synthesis routes of the sulfide solid electrolyte, which have resulted in notable improvements. At the anode/electrolyte interface, lithium dendrite formation and interfacial reactions between lithium metal and the sulfide solid electrolyte are the most notable challenges. Using artificial solid electrolyte interfaces with a low electronic conductivity, employing an alloy anode, and synthesizing composite electrolytes are typical approaches for overcoming these problems. In addition, from the perspective of the practical production of sulfide-based all-solid-state lithium batteries, electrode/electrolyte membrane-forming technology and the assembly of pouch cells are introduced. Membrane-forming technology has gained extensive attention with the aim of fabricating thin and mechanically stronger solid electrolyte membranes. High-loading cathode membranes as well as solid electrolyte membranes, dry processing, and wet processing are reviewed. Moreover, the improvement in the solid-solid contact of pouch cells, the design of high-loading cathodes, and the low-cost and scaled up production of sulfide solid electrolytes are introduced. Finally, we also propose research directions and future development trends for sulfide-based all-solid-state lithium batteries.
