Acid-scavenging separators promise long-term cycling stability of lithium-ion batteries

Acidification of traditional commercial electrolytes arising from LiPF₆ degradation severely affects the long-term durability of lithium-ion batteries. In particular, the moisture introduced during battery fabrication and operation leads to hydrogen fluoride generation and triggers a series of parasitic reactions, resulting in the decomposition of a solid electrolyte interphase and the structure destruction of electrodes. Acid-scavenging separators are a promising option to solve the above problems without changing the existing electrode and electrolyte preparation industries, especially for widely applied lithium-ion batteries using LiPF₆-containing electrolytes. So far, various advanced acid-scavenging separators have been developed, but there is no comprehensive review that systematically elucidates the importance of acid-scavenging separators. In this review, the mechanism of LiPF₆ degradation on the acidification of traditional commercial electrolytes is firstly discussed from the perspective of internal battery components. Subsequently, the acid removal mechanism, electrochemical characteristics, and long-cycle performance of the acid-removing separators are summarized. Further developments and challenges of the acid-scavenging separators are outlined. Finally, future applications and research directions of the acid-scavenging separators are proposed.