Dynamic Ion Sieve as the Buffer Layer for Regulating Li+ Flow in Lithium Metal Batteries

How to realize uniform Li+ flow is the key to achieve even Li deposition for lithium metal batteries (LMBs). In this study, a concept of dynamic ion sieve is proposed to design the buffer layer nearby Li anode surface to regulate Li+ spatial arrangement by introducing tributylmethylphosphonium bis(trifluoromethanesulfonyl)imide (TMPB) into the carbonate electrolyte. The buffer layer induced by TMP+ can adjust the velocity of arriving solvated Li+ that gives solvated Li+ sufficient time to redistribute and accumulate on Li anode surface, resulting in a uniform and higher concentrated Li+ flow. Besides, TFSI- can participate in the generation of inorganic component-rich solid electrolyte interphase (SEI) with Li3N, which can facilitate the Li+ conductivity of SEI. Consequently, the stable and uniform Li deposition can be obtained, achieving the excellent cycling performance up to 1000 h at 0.5 mA cm(-2) in the Li||Li symmetric cell. Besides, the Li||NCM622 full cell also possesses excellent cycling stability with a high-capacity retention rate of 66.7% after 300 cycles.

Automated summary

Realizing uniform Li+ flow is crucial for achieving even Li deposition in lithium metal batteries (LMBs). In this study, a dynamic ion sieve concept is proposed, which involves designing a buffer layer near the Li anode surface to regulate Li+ spatial arrangement by introducing TMPB into the carbonate electrolyte. The buffer layer induced by TMP+ allows solvated Li+ sufficient time to redistribute and accumulate on the Li anode surface, resulting in a uniform and concentrated Li+ flow. Additionally, TFSI- participates in the formation of an inorganic-rich solid electrolyte interphase (SEI) with Li3N, enhancing the Li+ conductivity of the SEI. As a result, the stable and uniform Li deposition achieved excellent cycling performance in Li||Li symmetric cells for up to 1000 hours at 0.5 mA cm(-2). Furthermore, the Li||NCM622 full cell exhibited excellent cycling stability with a high-capacity retention rate of 66.7% after 300 cycles.