Protic and Aprotic Ionic Liquids in Combination with Hard Carbon for Lithium‐Ion and Sodium‐Ion Batteries

Abstract In this work we report the use of the aprotic ionic liquid 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr 14 TFSI) and the protic ionic liquid 1‐butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr H4 TFSI) in combination with olive pits derived hard carbon electrodes in view of the realization of advanced Li‐ion and Na‐ion batteries. We show that in the case of Li‐based systems both classes of ionic liquids can be successfully utilized at room‐temperature to build high performance and stable hard carbon‐based systems. In the case of Na‐ion chemistry, Pyr 14 TFSI appears very promising while the use of Pyr H4 TFSI is not applicable due to the lack of electrochemical stability below 1 V vs. Na/Na + .