Intercalation chemistry engineering strategy enabled high mass loading and ultrastable electrodes for...

Aqueous electrochemical energy storage devices (AEESDs) are considered one of the most promising candidates for large-scale energy storage infrastructure due to their high affordability and safety. Developing electrodes with the merits of high energy density and long lifespan remains a challenging issue toward the practical application of AEESDs. Research attempts at electrode materials, nanostructure configuration, and electronic engineering show the limitations due to the inherent contradictions associated with thicker electrodes and ion-accessible kinetics. Herein, we propose an intercalation chemistry engineering strategy to enhance the electrolyte ion (de)intercalation behaviors during the electrochemical charge-discharge. To validate this strategy, the prototypical model of a high-mass-loading MnO₂-based electrode is used with controlled intercalation of Na⁺ and H₂O. Theoretical and experimental results reveal that an optimal content of Na⁺ and H₂O on the MnO₂-based electrode exhibits superior electrochemical performance. Typically, the resultant electrode exhibits an impressive areal capacitance of 1551 mF/cm² with a mass loading of 9.7 mg/cm² (at 1 mA/cm²). Furthermore, the assembled full-cell with obtained MnO₂-based electrode delivers a high energy density of 0.12 mWh/cm² (at 20.02 mW/cm²) and ultra-high cycling stability with a capacitance retention percentage of 89.63 % (345 mF/cm²) even after 100,000 cycles (tested over 72 days).