Lithium salts with low coordinating anions such as bis(trifluoromethanesulfonyl)imide (TFSI) have been the state‐of‐the‐art for polyethylene oxide (PEO)‐based “dry” polymer electrolytes for 3 decades. Plasticizing PEO with TFSI‐based ionic liquids (ILs) to form ternary solid polymer electrolytes (TSPEs) increases conductivity and Li+ diffusivity. However, the Li+ transport mechanism is unaffected compared to their “dry” counterparts and is essentially coupled to the dynamics of the polymer host matrix, which limits Li+ transport improvement. Thus, a paradigm shift is hereby suggested: the utilization of more coordinating anions such as trifluoromethanesulfonyl‐N‐cyanoamide (TFSAM), able to compete with PEO for Li+ solvation, to accelerate the Li+ transport and reach a higher Li+ transference number. The Li–TFSAM interaction in binary and ternary TFSAM‐based electrolytes is probed by experimental methods and discussed in the context of recent computational results. In PEO‐based TSPEs, TFSAM drastically accelerates the Li+ transport (increases Li+ transference number by a factor 6 and the Li+ conductivity by 2–3) and computer simulations reveal that lithium dynamics are effectively re‐coupled from polymer to anion dynamics. Last, this concept of coordinating anions in TSPEs is successfully applied in LFP||Li metal cells leading to enhanced capacity retention (86% after 300 cycles) and an improved rate performance at 2C.

A new asymmetrical anion, trifluoromethanesulfonyl-N-cyanoamide (TFSAM -), was paired with Nbutyl-N-methyl pyrrolidinium (PYR14 + ) to prepare PYR14TFSAM. It has been investigated for Li-ion battery application and compared to its PYR14 + analogs paired with either the dicyanamide anion (DCA -) or other anions (i.e. bis(trifluoromethanesulfonyl) imide (TFSI -), bis(fluorosulfonly)imide (FSI -), trifluoromethanesulfonyl-fluorosulfonyl imide (FTFSI -)). The conductivity of PYR14TFSAM is not only higher than that of PYR14TFSI, but also higher than that of PYR14FTFSI with 3.8 mS cm -1 at 20°C and 12.6 mS cm -1 at 60°C. In addition, the ionic liquid does not crystallize and exhibits a viscosity similar to that of PYR14FSI (and even lower above 30°C, which also results in a higher conductivity at high temperature). Compared to PYR14DCA, PYR14TFSAM has a higher anodic stability, more compatible with state-of-the-art cathodes such as NCM, even though the PYR14DCA electrolyte also allowed surprisingly good cycling results of NCM cathode considering its low anodic stability. PYR14TFSAM also allows Li + (de-)/insertion into graphite, using vinylene carbonate as additive. When used in conventional Li-ion electrolyte solvents, it leads to moderate conductivity (as compared with LiFSI or LiTFSI), although much higher than LiDCA. Additionally, it is shown that, even in EC/DMC-based electrolyte, LiTFSAM does not induce Al corrosion at 4.2V.

In state-of-the-art lithium-ion battery, sustainability and safety often have been ‘sacrificed’ in favor of the ‘performance’ and ‘cost’. Regarding the electrolyte, volatile and flammable solvents and highly toxic fluorinated lithium...