Non‐Flammable Fluorinated Phosphorus(III)‐Based Electrolytes for Advanced Lithium‐Ion Battery Performance

Abstract

In the quest for ever higher energy and power densities of lithium‐based batteries, numerous functional materials are being utilized, however in many cases their highly reactive nature is likely to increase the risk of danger in case of battery failures. This especially affects the aprotic non‐aqueous organic carbonate‐based electrolyte, still considered as the state‐of‐the‐art (SOTA) and its volatile and highly flammable components. Efforts to identify different forms of flame‐retardants or nonflammable electrolyte solvents/co‐solvents to reduce the risk of fire or explosion are inevitably followed by a trade‐off between the improved safety and deteriorated overall cycling performance of a battery. Here, we report on a smartly tailored, multifunctional nonflammable electrolyte formulation comprising 15.0 wt.% 2‐(2,2,3,3,3‐pentafluoro‐propoxy)‐4‐(trifluormethyl)‐1,3,2‐dioxaphospholane (PFPOEPi‐1CF3), significantly advancing the cycling performance of the NMC111||graphite cells by formation of an effective interphase on/at both anode and cathode and correlate its performance to the 2‐(2,2,3,3,3‐pentafluoropropoxy)‐1,3,2‐dioxaphospholane (PFPOEPi) containing electrolyte counterpart by establishing a strong structure‐reactivity‐performance‐relationship.

Face to Face at the Cathode Electrolyte Interphase: From Interface Features to Interphase Formation and Dynamics

“…An additional merit of fluorine containing additives as part of an electrolyte is their tendency to combust rather than to catch fire. [130] Fluorinated electrolytes have been demonstrated to help reaching new levels of performance and safety in high voltage batteries. [131][132][133][134][135][136][137] In case of high voltage application, the substitution of hydrogen with fluorine atoms leads to reduced activation energy [138] and decreased HOMO and LUMO energy levels, thus resulting in increased reduction and decreased oxidation potentials.…”

“…In this respect, design and development of multifunctional additives or mixtures of at least two carefully selected functional additives seems to be a more effective approach. [130,149,[155][156][157][158]…”

Aromatic heterocyclic anion based ionic liquids and electrolytes

“…5,6 Several attempts have been made to use nonflammable solvents, thermally and electrochemically stable (non-fluorinated) Li-salts, as well as additives to improve safety. [7][8][9][10][11][12] There is an urge to develop new salts and solvents with beneficial physical and chemical properties that can potentially replace the conventional fluorinated electrolytes.…”

Electrolytes: From a Thorn Comes a Rose, and from a Rose, a Thorn

“…Considerable progress and new concepts in respect to the advanced electrolyte formulations and active materials have been achieved leading to electrochemical systems with long life, high energy density, high power and adequate safety at competitive manufacturing cost. [31,[61][62] Manuscripts reporting novel electrolytes and/or advancement of existing formulations are appearing in large numbers literally every day, thus providing further insight into already reported materials. For example, current liquid electrolyte formulations, fulfilling a wide variety of important requirements primarily including a broad electrochemical stability window, a wide liquid range, a high thermal stability, a low vapor pressure, a low viscosity, a high lithium ion conductivity, a high capacity as well as high cycling rates, are result of perennial, however still ongoing research and development processes.…”

“…Due to the tremendously increasing research interest in electrochemical energy storage worldwide, the available literature in the field of electrolytes is steadily increasing; this is particularly true for lithium ion conducting electrolytes. Considerable progress and new concepts in respect to the advanced electrolyte formulations and active materials have been achieved leading to electrochemical systems with long life, high energy density, high power and adequate safety at competitive manufacturing cost [31,61–62] . Manuscripts reporting novel electrolytes and/or advancement of existing formulations are appearing in large numbers literally every day, thus providing further insight into already reported materials.…”