Mn-Doped NiMoO₄ Mesoporous Nanorods/Reduced Graphene Oxide Composite for High-Performance All-Solid-State Supercapacitor

Abstract

Mn-doping has great influence on the structural and electrical properties of NiMoO4, which plays an important role in determining its electrochemical activities. In this work, Mn-doped NiMoO4 was prepared. Structural characterization and theoretical calculation reveal that Mn-doped NiMoO4 (Mn0.1Ni0.9MoO4) has smaller unit cell parameters and is more reactive than NiMoO4 because of the defects produced by Mn-doping. On the basis of that, we prepared a composite consisting of Mn0.1Ni0.9MoO4 mesoporous nanorods and reduced graphene oxide (Mn0.1Ni0.9MoO4/rGO), which was assembled into a symmetrical all-solid-state device as electrode material, with alkaline poly(vinyl alcohol) as solid-state electrolyte. The device shows a good specific capacitance of 109.3 F·g–1 at 1 A·g–1 in a rather wide voltage range of 0–1.8 V, exhibits an excellent cycling stability with 96.1% of the capacitance retained after 200 cycles, and delivers a high energy density of 49.2 Wh·kg–1 at 1800 W·kg–1. The all-solid-state supercapacitor owns superior flexibility and maintains 83.6% of its initial specific capacitance under the bent condition. When tested in a three-electrode system, the Mn0.1Ni0.9MoO4/rGO composite exhibits a maximum specific capacitance of 688.9 F·g–1 at 0.5 A·g–1 that is much better than NiMoO4 and Mn0.1Ni0.9MoO4. The results show that the Mn0.1Ni0.9MoO4/rGO composite stands out as a kind of transition-metal-doped electrode material for flexible all-solid-state supercapacitors.