Crystalline Co 2 V 3 O 8 @Amorphous Co−B Core‐Shell Nano‐Microsphere: Tunable Shell Layer Thickness, Faradaic Pseudocapacitive Mechanism, and Electrochemical Capacitor Applications

The interface engineering of highly efficient electrode materials is of dominant importance for enhancing the electrochemical performance of advanced energy storage devices. Here, we demonstrate the construction of a novel crystalline@amorphous core‐shell nanostructured with Co 3 V 2 O 8 spherical particles as the cores and Co−B nanoflakes as the shells. The Co−B shell layer thickness could be tuned by changing the mass ratio of Co 3 V 2 O 8 and B source. This unique structure shows intriguing synergistic properties with increased electroactive sites and also provides effective space and a short diffusion distance for faradaic reactions. The tunable amorphous layer facilitates the electrolyte diffusion while showing elastic behavior to alleviate the volume strain of Co 3 V 2 O 8 , and also provides a path for electron transport. The resulting Co 3 V 2 O 8 @Co−B under optimum conditions exhibits a high specific capacitance, remarkable rate performance, and outstanding cycling stability. Such an effective redox approach may shed substantial light on inspiring crystalline/amorphous contacts and their derivatives for energy storage and conversion devices.