2D˗on˗2D vertically–horizontally oriented SnS2˗Ti3C2Tx MXene heterostructures with sulfur vacancies for high-energy asymmetric supercapacitors

Rationally designed heterostructures hold significant promise for next-generation energy storage devices because their synergistically integrated features generally outperform those of pristine materials. However, achieving rational heterostructure design with precise structural control remains a major challenge that limits the electrochemical potential. In this study, well-defined vertically aligned two-dimensional (2D) SnS 2 nanosheets were anchored onto horizontally oriented 2D Ti 3 C 2 T x MXene microflakes to form a 2D-on-2D heterostructure. The inherently low electrical conductivity of SnS 2 was effectively addressed through sulfur vacancy (S v ) engineering, resulting in highly energetic vertical–horizontal 2D˗on˗2D S v –SnS 2 –Ti 3 C 2 T x MXene heterostructures. Density functional theory calculations confirmed the enhanced electronic conductivity and strong Na + adsorption, which facilitated rapid ion transport and superior electrochemical performance. These synergistic effects optimized the S v –SnS 2 –Ti 3 C 2 T x MXene heterostructure, exhibiting high specific capacitance (706 F g -1 at 2 A g -1 ) and excellent cycling stability. The assembled asymmetric supercapacitor, employing S v –SnS 2 –Ti 3 C 2 T x MXene as the cathode and Ti 3 C 2 T x MXene as the anode, delivered an exceptional energy density of 58.33 Wh kg -1 at a power density of 800 W Kg -1 , while retaining ~96% of its capacitance after 10,000 cycles. This study presents a scalable strategy for constructing defect-engineered 2D˗on˗2D heterostructures, thereby advancing the development of next-generation high-performance energy storage devices. This study highlights well-defined, vertically aligned two-dimensional (2D) SnS 2 nanosheets anchored on horizontally oriented 2D Ti 3 C 2 T x MXene microflakes to form a robust 2D-on-2D heterostructure. Sulfur vacancy (S v ) engineering significantly enhances the SnS 2 electrical conductivity, enabling highly energetic 2D-on-2D S v –SnS 2 –Ti 3 C 2 T x MXene heterostructures with high electrochemical energy storage performance