Cation vacancy-driven structural modulation across scales in MXene/Zn(v)Mn2Se4 for enhanced supercapacitor performance

Abstract

Cationic vacancy engineering boosts electrode kinetics and ion transport by fine-tuning active sites and charge conduction routes. This provides a new way to balance the contradiction between the high specific capacity and the power/energy density of asymmetric supercapacitors (ASCs). The study presents a cross-scale structural modulation strategy for ZnMn₂Se₄ with zinc cation vacancies (Zn_(v)Mn₂Se₄) through synergistic calcination and two-step etching methodologies. The innovative approach enables precise conversion of unique 1D-ZIF templates into metal selenides with tailorable vacancy configurations, achieved through the synergistic combination of macroscopic morphological engineering and atomic-level defect manipulation. Moreover, the MXene/Zn_(v)Mn₂Se₄ composite demonstrates exceptional specific capacitance (2093.4 F g⁻¹ at 1 A g⁻¹) through synergistic coupling of cationic vacancy engineering and conductive MXene integration, where the engineered metal vacancies enhance electroactive sites density while the MXene-induced heterointerface optimizes electrolyte infiltration kinetics. Furthermore, the self-made biomass carbon-based asymmetric supercapacitor biomass charcoal (BC)//MXene/Zn_(v)Mn₂Se₄ delivers 744.97 W kg⁻¹ power density and 112.39 Wh kg⁻¹ energy density. By harmonizing high energy-power density with long-term charge stability in low-mass electrodes, this work unveils an environmentally benign approach that bridges the gap between laboratory innovation and market-ready ASC technologies.