Sodium Naphthalene‐2,6‐dicarboxylate: An Anode for Sodium Batteries

The conjugated dicarboxylate sodium naphthalene‐2,6‐dicarboxylate (Na2NDC) was prepared by a low‐energy‐consumption reflux method, and its performance as a negative electrode for sodium‐ion batteries was evaluated in electrochemical cells. The structure of Na2NDC was solved for the first time (monoclinic P21/c) from powder XRD data and consists of π‐stacked naphthalene units separated by sodium–oxygen layers. Through an appropriate choice of binder and conducting carbon additive, Na2NDC exhibited a reversible two electron sodium insertion at approximately 0.4 V (vs. Na+/Na) with remarkably stable capacities of approximately 200 mAh g−1 at a rate of C/2 and good rate capability (≈133 mAh g−1 at 5 C). In parallel, the high thermal stability of the material was demonstrated by high‐temperature XRD: the framework remained intact to above 500 °C.