Solvation Design of an Interfacial Self‐Compatible Quasi‐Solid Electrolyte for High‐Loading Sodium‐Based Dual‐Ion Batteries

Abstract Sodium‐based dual‐ion batteries (SDIBs) attract extensive attention in stationary energy storage for their low cost, environmental friendliness, and high working voltage. However, traditional liquid electrolytes for SDIBs undergo solvent co‐intercalation and severe oxidation decomposition at high voltage, causing unstable cathode structure and low Coulombic efficiency, especially with high loading (>5 mg cm −2 ). Herein, an interfacial self‐compatible quasi‐solid electrolyte (ACPE) is developed via an additive‐induced solvation design strategy. The additive exhibits stronger coordination with Hexafluorophosphate anion (PF 6 − ) than ethyl methyl carbonate (EMC) molecules, prevents solvent co‐intercalation, and decomposes preferentially to form a thin and robust cathode‐electrolyte interphase (CEI). ACPE offers a high oxidation stability (5.5 V) and effectively curbs solvent co‐intercalation at the graphite cathode. On the sodium anode, an ACPE‐derived robust interphase enables stable sodium plating/stripping for over 300 h. Consequently, for the first time, an in situ fabricated quasi‐solid SDIB with high loading (>6.0 mg cm −2 ) demonstrates stable cycling performance (above 900 cycles) and a commendable rate capability (84.6% capacity retention at 10 C), among the best quasi‐solid DIBs. Even with an ultra‐high‐loading cathode (>16.0 mg cm −2 ), the SDIB maintains a stable capacity for 300 cycles. This solvation strategy of electrolytes paves a new way for developing high‐loading DIBs.