Advancing lithium metal batteries with in situ polymerized PMMA-based elastomericelectrolytes

A novel denture-inspired protocol for the preparation of poly(methyl methacrylate) (PMMA)-based solid-state elastomer electrolytes for lithium metal batteries (LMBs) has been reported in this work. The combination of succinonitrile and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a deep eutectic electrolyte (DEE) enables efficient dissociation of Li⁺ from TFSI^-. Additionally, by optimizing the molar ratios of DEE and MMA to 2.16 : 1, an elastomeric electrolyte with a "polymer-in-salt" structure was developed, featuring continuous pathways for fast Li⁺ transport and high ionic conductivity (i.e., 0.497 mS cm^-1 at 30 °C). The multi-level structure of the ion transport pathways was elucidated through a combination of electron microscopy, small-angle X-ray scattering and Raman spectroscopy data. Moreover, utilizing in situ polymerization, robust adhesion between the electrolyte and solid electrodes was achieved, facilitating efficient Li⁺ transfer and stable solid-electrolyte interface layer formation. These electrolytes demonstrate excellent compatibility and stability with high-voltage cathodes and Li anodes, as evidenced by the superior cycling performance of LMBs. These findings provide significant insights into the design and development of new solid-state polymer electrolytes, advancing the commercial application of LMBs.