A High Performing Conjugated Microporous Polymer Cathode for Practical Sodium Metal Batteries Using an Ammoniate as Electrolyte

The development of room‐temperature sodium‐metal batteries (SMBs) presents a cost‐effective solution for both large‐scale energy storage and high‐energy applications. However, challenges in finding suitable electrolytes that ensure stable cycling of the Na metal anode and the lack of cathodes capable of achieving high‐performance under practical conditions have impeded their commercialization. In this study, a high‐performance SMB combining a concentrated liquid ammonia‐based electrolyte (NaI·3.3NH3) and an organic cathode featuring an anthraquinone‐based conjugated microporous polymer hybrid (IEP‐11‐SR) are introduced. This ammoniate electrolyte effectively stabilizes the sodium anode, allowing reversible plating/stripping and preventing dendrite formation, even at extreme current densities (400 mA cm−2). The hybrid polymer cathode, with its intrinsic extended conjugated and microporous structure, exhibits outstanding electrochemical performance in rate‐capability and long‐term cyclability in the ammoniate electrolyte. The resulting SMB achieves a high capacity (100 mAh g−1 at 1C), excellent rate capability (51 mAh g−1 at 250C), and stable cycling performance (≈70% capacity retention after 4000 cycles at 15C). Notably, the utilization of remarkably thick cathodes (60 mg cm−2) with low carbon content (≈20 wt%) achieves an unprecedented areal capacity, close to 7 mAh cm−2, marking a significant advancement in practical SMB technology. This work demonstrates the outstanding electrochemical performance of a sodium metal battery based on a conjugated microporous polymer cathode and ammoniate electrolyte. This battery exhibits long‐term cyclability (4000 cycles), excellent rate capability (52% capacity retention at 250C), and an unprecedented areal capacity (7 mAh cm−2).