V₂CT_X MXene Sphere for Aqueous Ion Storage

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 V₂CT_X flakes utilizing a carbon sphere template (V₂CT_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 V₂CT_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 V₂CT_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_V2CTX⁻¹ at 0.5 A g⁻¹ and remains at 122 mAh g_V2CTX⁻¹ at 18 A g⁻¹. With a 0.95-V voltage plateau, the energy density of 330.4 Wh kg_V2CTX⁻¹ surpasses previous records of aqueous MXene electrodes.