Stabilizing the Li1.3 Al0.3 Ti1.7 (PO4 )3 |Li interface for high efficiency and long lifespan quasi-solid-state lithium metal batteries

To tackle the poor chemical/electrochemical stability of Li1+x Alx Ti2-x (PO4 )3 (LATP) against Li and poor electrode|electrolyte interfacial contact, a thin poly[2,3-bis(2,2,6,6-tetramethylpiperidine-N-oxycarbonyl)norbornene] (PTNB) protection layer is applied with a small amount of ionic liquid electrolyte (ILE). This enables study of the impact of ILEs with modulated composition, such as 0.3 lithium bis(fluoromethanesulfonyl)imide (LiFSI)-0.7 N-butyl-N-methylpyrrolidinium bis(fluoromethanesulfonyl)imide (Pyr14 FSI) and 0.3 LiFSI-0.35 Pyr14 FSI-0.35 N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14 TFSI), on the interfacial stability of PTNB@Li||PTNB@Li and PTNB@Li||LiNi0.8 Co0.1 Mn0.1 O2 cells. The addition of Pyr14 TFSI leads to better thermal and electrochemical stability. Furthermore, Pyr14 TFSI facilitates the formation of a more stable Li|hybrid electrolyte interface, as verified by the absence of lithium "pitting corrosion islands" and fibrous dendrites, leading to a substantially extended lithium stripping-plating cycling lifetime (>900 h). Even after 500 cycles (0.5C), PTNB@Li||LiNi0.8 Co0.1 Mn0.1 O2 cells achieve an impressive capacity retention of 89.1 % and an average Coulombic efficiency of 98.6 %. These findings reveal a feasible strategy to enhance the interfacial stability between Li and LATP by selectively mixing different ionic liquids.