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 (PF₆ ^-) 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.