Vanadium Solid‐Solution Engineered Mo 2 CT z MXene Nanoarchitectonics for High‐Performance Zn‐Ion Hybrid Supercapacitors

Abstract 2D Mo‐based MXenes are highly promising electrode materials for Zn‐ion hybrid supercapacitors (ZHSCs). However, their exposed reversible redox active sites are insufficient, which limits the ion diffusion rate and charge storage behaviors. Herein, a newly designed 2D V‐doped Mo 2 CT z (solid‐solution MXene) nanoarchitectonics with a tunable V content are prepared via a two‐step molten salt process. V sites occupy the initial sites of Mo, triggering charge transfer and thereby activating the basal plane. Increasing the introduced amount of V element can produce more defects to expose more active sites and form amorphous structures to support multiple reaction pathways. Meanwhile, the incorporation of V with rich redox valence states introduces pseudocapacitive active sites, accelerates charge transfer rates, and thus boosts electrochemical performance. As a result, the optimized (Mo 1/3 V 2/3 ) 2 CT z electrode exhibits substantially improved Zn‐ion storage capacity, which delivers high gravimetric capacitance of 608.6 F g −1 at 0.2 A g −1 , excellent capacity retention rate of 94.4% after 13 000 cycles, as well as a comparable energy density of 91.8 Wh kg −1 at a power density of 104.2 W kg −1 . Furthermore, two button cells based on the (Mo 1/3 V 2/3 ) 2 CT z can be integrated in series to light up a red LED indicator.