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. Acid-scavenging separators are an efficient way to inhibit the acidification of traditional LiPF6-containing electrolytes. This paper reviews the development and achievements of acid-scavenging separators to enhance their practical application capabilities and future developments.