Interface Engineering with an Organic Aluminum Additive for High-Rate Sodium Metal Batteries

Interface stability is a key to practical applications of high-rate sodium metal batteries (SMBs). The general sodium metal anode (SMA), for example, suffers from an unstable solid electrolyte interface (SEI), which may induce severe dendrite growth and continuous Na consumption, particularly under high rates. At the same time, the cathode electrolyte interface (CEI) of a widely adopted cathode material Na₃V₂(PO₄)₃ (NVP) has to tolerate the massive volume changes during the rapid Na⁺ ion intercalation/extraction, resulting in structural degradations and the capacity loss. Here, a facile strategy is reported by introducing aluminum ethoxide to a conventional ether-based electrolyte, to promote the formation of an alumina-rich SEI and CEI, which facilitates the rapid Na⁺ ion transport across the interface and promotes the uniform Na deposition. The resultant Na || Na symmetric cell demonstrates a stable cycling of 4800 h at 10 mA cm⁻² and 1 mAh cm⁻², and a Na || NVP full cell exhibits a high capacity retention of 81.28% after 6000 cycles at 40C. The simultaneous interface engineering of both the Na metal anode and the NVP cathode via the facile organic aluminum additive opens up a new avenue toward practical application of high-rate SMBs.