In-Situ Implanted\nRobust and Durable Cathode-Electrolyte\nInterphase for High-Performance Sodium-Based Dual-Ion Batteries

The\npractical applications of economically viable and\nenvironmentally\nfriendly sodium-based dual-ion batteries (Na-DIBs) are currently restricted\nbecause of the short life spans of these systems. The development\nof a robust and durable cathode–electrolyte interphase (CEI)\nlayer is expected to serve as an effective measure to enhance the\ncycling performances of Na-DIBs. Herein, a high charging voltage is\nemployed during precycling to decompose sodium difluoro(oxalato)borate\n(NaDFOB) on an expanded mesocarbon microbead (HRO-MCMB) cathode surface,\nthereby promoting the formation of an inorganic-rich CEI layer. This\nCEI layer not only serves as a chemically stable and mechanically\nstrong barrier but also effectively inhibits the volume expansion\nand exfoliation of the cathode graphite layer. Consequently, the HRO-MCMB\ncathode modified with 0.02 M NaDFOB exhibited a capacity retention\nof 97.0% after 1000 cycles at a current density of 1 C. The HRO-MCMB(+)||HC(−)\n(HC = hard carbon) full cell maintained a specific capacity of 110.9\nmAh g<sup>–1</sup> after 300 cycles at 1 C. Furthermore, the\nNa-DIB full cell exhibited an impressive energy density of up to 422.6\nWh kg<sup>–1</sup>, and its maximum power density reached 4682.9\nW kg<sup>–1</sup>. Overall, this study provides a novel strategy\nfor the practical development of high-performance Na-DIBs.