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, we introduce 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). 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.