Effects of lithium salts on PEO-based solid polymer electrolytes and their all-solid-state lithium-ion batteries

For all-solid-state lithium-ion batteries (ASSBs), they have two key parameters including ionic conductivity and interfacial properties. Considering the previous studies focused more on single property, we aimed to investigate the effects of lithium salts on comprehensive properties of PEO-based SPEs and find out the optimal lithium salts. For the SPE with LiTFSI, it has the highest ionic conductivity (5.3 \(\times\) 10−6 S cm−1 at 25 °C and 2.4 \(\times\) 10−4 S cm−1 at 60 °C) and discharge capacity, mainly due to the lowest crystallinity and the highest lithium-ion transference number. For the SPE with LiFSI, it has the best interfacial properties and cycling performance, mainly due to the denser and flatter LiF SEI layer after cycling. Our work indicates that as for PEO-based ASSBs, LiTFSI can be used to get higher discharge capacities, and LiFSI can be used to get higher retention rate.