Composite Cathodes for Solid-State Lithium Batteries: Catholytes the Underrated Giants

To expedite the large-scale adoption of electric vehicles (EVs), increasing the gravimetric energy density of batteries to at least 250 Wh kg(-1) while sustaining a maximum cost of $120 kWh(-1) is of utmost importance. Solid-state lithium batteries are broadly accepted as promising candidates for application in the next generation of EVs as they promise safer and higher-energy-density batteries. Nonetheless, their development is impeded by many challenges, including the resistive electrode-electrolyte interface originating from the removal of the liquid electrolyte that normally permeates through the porous cathode and insures efficient ionic conductivity through the cell. One way to tackle this challenge is by formulating composite cathodes (CCs) that employ solid ionic conductors as catholytes in their structure. Herein, it is attempted to shed light on this less studied and poorly understood approach. The different classes of catholytes that have been reported in literature alongside the most common fabrication techniques used to prepare CCs are presented. Next, the interplay between the microstructure and design parameters of CCs with the electrochemical performance of solid-state batteries (SSBs) and the techniques used to measure their transport properties is well documented. Finally, general guidelines surrounding CC research are outlined.

Automated summary

To promote the widespread use of electric vehicles, it is crucial to increase the energy density of batteries while keeping the cost low. Solid-state lithium batteries are considered promising candidates for the next generation of electric vehicles due to their safety and high energy density. However, the development of these batteries is hindered by challenges such as the resistive interface between the electrode and electrolyte. One approach to address this challenge is by using composite cathodes (CCs) that incorporate solid ionic conductors. This article provides an overview of different types of catholytes used in CCs and the common techniques for fabricating them. It also discusses the relationship between the microstructure and design parameters of CCs and the electrochemical performance of solid-state batteries, as well as the methods used to measure their transport properties. Finally, general guidelines for CC research are outlined.