Polymeric Schiff Bases as Low‐Voltage Redox Centers for Sodium‐Ion Batteries

The redox entity comprising two Schiff base groups attached to a phenyl ring (NCHArHCN) is reported to be active for sodium‐ion storage (Ar=aromatic group). Electroactive polymeric Schiff bases were produced by reaction between non‐conjugated aliphatic or conjugated aromatic diamine block with terephthalaldehyde unit. Crystalline polymeric Schiff bases are able to electrochemically store more than one sodium atom per azomethine group at potentials between 0 and 1.5 V versus Na + /Na. The redox potential can be tuned through conjugation of the polymeric chain and by electron injection from donor substituents in the aromatic rings. Reversible capacities of up to 350 mA h g −1 are achieved when the carbon mixture is optimized with Ketjen Black. Interestingly, the “reverse” configuration (CHNArNHC) is not electrochemically active, though isoelectronic.