Dual fluorination of polymer electrolyte and conversion-type cathode for high-capacity all-solid-state lithium metal batteries

All-solid-state batteries are appealing electrochemical energy storage devices because of their high energy content and safety. However, their practical development is hindered by inadequate cycling performances due to poor reaction reversibility, electrolyte thickening and electrode passivation. Here, to circumvent these issues, we propose a fluorination strategy for the positive electrode and solid polymeric electrolyte. We develop thin laminated all-solid-state Li||FeF3 lab-scale cells capable of delivering an initial specific discharge capacity of about 600mAh/g at 700mA/g and a final capacity of about 200mAh/g after 900 cycles at 60 degrees C. We demonstrate that the polymer electrolyte containing AlF3 particles enables a Li-ion transference number of 0.67 at 60 degrees C. The fluorinated polymeric solid electrolyte favours the formation of ionically conductive components in the Li metal electrode's solid electrolyte interphase, also hindering dendritic growth. Furthermore, the F-rich solid electrolyte facilitates the Li-ion storage reversibility of the FeF3-based positive electrode and decreases the interfacial resistances and polarizations at both electrodes.

Automated summary

All-solid-state batteries are promising due to their high energy content and safety, but their practical development is hindered by poor cycling performance and electrode passivation. In this study, a fluorination strategy is proposed to address these issues, and thin laminated all-solid-state batteries with excellent cycling performance are developed.