Sodium preintercalation-induced oxygen-deficient hydrated potassium manganese oxide for high-energy flexible Mg-ion supercapacitors

Abstract Layered potassium manganese oxides are promising candidates for use in aqueous supercapacitors owing to their wide potential windows, layered feature, and Faradaic redox reactions that occur on surfaces bulk regions. However, the practical application is hindered by rapid performance degradation due inherently low electrical conductivities inferior structural stabilities. Here, we develop ultralong nanobelts comprising hydrated Na-intercalated oxygen-deficient oxide (H-Na-D-KMO), which Na + ions preintercalated synchronously induce generation of oxygen vacancies, as high-energy-density durable electrodes Mg-ion supercapacitors. The experimental results indicated preintercalation formation vacancies improved properties ion diffusion, accounted fast reaction kinetics good cycling H-Na-D-KMO. optimized H-Na-D-KMO delivered a significantly enhanced specific capacitance compared those pure H-KMO. Asymmetric with cathode as-prepared MoO 2 @carbon anode exhibited an ultrahigh energy density 108.4 Wh kg –1 at 11,000 −1 , superior most reported literature. Moreover, assembled device stability over 5000 cycles fading rate 0.002% per cycle mechanical flexibility, opens avenue further advancements high-energy