V 2 CT X MXene Sphere for Aqueous Ion Storage

Abstract

Despite the remarkable ion-hosting capability of MXenes, their electrochemical performance is restricted to the ion shuttle barrier stemming from the capacious surface and the sluggish chemical activity of intrinsic transition metal layers. Herein, we construct a vertically aligned array of V 2 CT X flakes utilizing a carbon sphere template (V 2 CT X @CS), with the interlayer galleries outward facing the external electrolyte, to shorten the diffusion length and mitigate the ion shuttle barrier. Moreover, we leverage the high sensitivity of V 2 CT X flakes to the water–oxygen environment, fully activating the masked active sites of transition metal layers in an aqueous environment via continuous electrochemical scanning. Aqueous V 2 CT X @CS/Zn battery delivers a novel capacity enhancement over 42,000 cycles at 10 A g −1 . After activation, the capacity reaches up to 409 mAh g V 2 CT X − 1 at 0.5 A g −1 and remains at 122 mAh g V 2 CT X − 1 at 18 A g −1 . With a 0.95-V voltage plateau, the energy density of 330.4 Wh kg V 2 CT X − 1 surpasses previous records of aqueous MXene electrodes.