Flame‐Retardant Additive/Co‐Solvent Contained in Organic Solution for Safe Second Batteries: A Review

Abstract

With the increased demands of energy density boosting the electrochemical performance of the rechargeable alkali metal ion batteries, the safe operation of second batteries is attracting much attention and needs to be especially considered during their further development, which is essential in view of the well‐known fire incidents of the lithium‐ion batteries. These dangerous events in the lithium‐ion batteries are as a consequence of the exothermic chemical reactions between the flammable carbonate‐based solutions and the electrode active material under the terrible working conditions. Under this circumstance, some series of flame‐retardant organic liquid‐based solutions have demonstrated the potential towards safer rechargeable batteries with the minimal injurious or the advantageous effect on the batteries’ performance. This article reviews the flame‐retardant organic liquid‐based solutions for the rechargeable batteries, providing the reader with an overview of the safe solutions with flame‐retardant additive/co‐solvent involving trimethyl phosphate and its derivative, P‐containing amide/phosphazene, all fluorinated solvent, and ionic liquids, in which the method of adapting concentrated and locally concentrated electrolyte solution are merged in the text content. Moreover, the functionality and purpose of the constituents in some flame‐retardant mixtures are discussed and many flame‐retardant electrolyte solutions are displayed to offer improved cycling and rate performance of different electrodes compared to traditional electrolyte solutions.

Enabling a non-flammable methyl(2,2,2-trifluoroethyl) carbonate electrolyte in NMC622–graphite Li-ion cells by electrode pre-passivation

“…A wide variety of novel liquid electrolytes for LIBs have been proposed, such as organophosphates, highly fluorinated molecules, and locally highly concentrated electrolytes. [1][2][3][4][5] A key consideration when substituting electrolyte components is the stability of the solid electrolyte interphase (SEI). The SEI is a surface layer on the graphite anode resulting from the passivation of the electrode surface.…”