A poly(ether block amide) based solid polymer electrolyte for solid-state lithium metal batteries

Solid-state lithium (Li) metal batteries (SSLMBs) with high-energy density and high-security are promising for energy storage application and electronic device development. However, Li dendrite generation is still one of the most important factors hindering the application of SSLMBs since interface contact degradation, dead Li accumulation, and continuous solid-electrolyte interphase (SEI) growth are always caused by Li dendrite growth, making the performances of SSLMBs deteriorate rapidly. In this study, a poly(ether block amide) (PEBA) based polymer electrolyte with lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI) as the Li salt is developed. It is found that the PEBA 2533-20% LiTFSI electrolyte possesses an ion conductivity of 3.0 × 10-5 S cm-1 at 25 °C. Especially, the Li dendrite suppression ability of SEI is greatly enhanced since it provides abundant amide groups to activate TFSI- anions and further enriches lithium fluoride (LiF) content in the SEI layer, which endows the full-cell with enhanced cyclability. As a result, the fabricated solid-state Li/PEBA 2533-20% LiTFSI/LiFePO4 (areal capacity: 0.15 mAh cm-2) battery remains 94% of its maximum capacity (127.5 mAh g-1) at a rate of 0.5C and 60 °C after 200 cycles. In particular, the full cell can cycle for almost 1000 times without short circuit. Therefore, the PEBA based electrolyte could promote the LiF enriched SEI layer into a platform to suppress the growth of Li dendrite toward SSLMBs with a long-life span.