Binder-free Mn–V–Sn oxyhydroxide decorated with metallic Sn as an earth-abundant supercapattery electrode for intensified energy storage

Abstract

The integration of battery and capacitor merits into one device would achieve the best energy storage performance. However, this is yet to be realized due to the difficulty in identifying enough supercapattery electrode materials. This study reports the fabrication of a binder-free, ternary metal oxyhydroxide composite based on earth-abundant Mn, V, and Sn (SMVS) metals as a potential electrode material for supercapacitor application. Deposition of the SO₄H-@Mn–V–Sn (SMVS) ternary metal oxyhydroxide composite directly on a treated nickel foam strip occurs via a one-step facile solvothermal method. The as-synthesized SMVS contains 2D nanosheets decorated with metallic Sn. The EDX analysis reveals the coexistence of all precursors in addition to sulfur. The FT-IR analysis indicates the presence of intercalated sulfate anions, which originate from vanadyl sulfate. The XPS analysis confirms the presence of Mn in multiple oxidation states (Mn²⁺, Mn³⁺, and Mn⁴⁺), V in the +4 oxidation state, and Sn in both +4 and 0 oxidation states, in addition to the presence of sulfur in the +6 oxidation state (SO₄H⁻). The as-fabricated ternary metal composite shows a high specific capacity of 2411.6 C g⁻¹ (5359.1 F g⁻¹) at 1.5 A g⁻¹ in 1 M KOH solution. The SMVS composite exhibits an outstanding rate capability of 67% at 15 A g⁻¹. The hybrid two-electrode device SO₄H⁻@Mn–V–Sn//hierarchical nitrogen-doped carbon (HDC) shows a wide operating potential window of 1.7 V without any parasitic reactions, achieving a high capacitance of 176.6 F g⁻¹ at 1.5 A g⁻¹ with an extremely high energy density of 70.9 W h kg⁻¹ and high specific power of 18 861.3 W kg⁻¹. Furthermore, the fabricated device shows superior cycling stability over 18 000 charge/discharge cycles with nearly 100% capacitance retention and coulombic efficiency.