Sodium ion-intercalated nanoflower 1T–2H MoSe2–graphene nanocomposites as electrodes for all-solid-state supercapacitors

TMDC have a unique layered structure that allows the insertion or extraction of various guest substances between layers, making them advantageous in energy storage. In this article, we demonstrate a sodium-intercalated electrode based on nanoflower 1T–2H MoSe2–graphene with an ultrahigh electrochemical performance for highly efficient energy storage applications. To increase the probability that ion insertion/extraction reactions occur inside the electrode material, we insert sodium ions into MoSe2–graphene material using a simple one-step hydrothermal method. Through density functional theory, we find that the insertion of sodium ions not only expands the distance between the layers to provide space for electrolyte ions but also moves the Fermi level closer to the conduction band, increasing the conductivity of MoSe2. The nanoflower structure provides a large specific surface area and increases the contact of ions with the surface of the material. The composite electrode has an ultrahigh capacity of 143.6 mAh g−1 at a current density of 0.5 A g−1. The all-solid-state supercapacitor makes with the composite electrode exhibits a superhigh power density of up to 3024 W kg−1.This study achieves an enhanced and efficient energy storage in a simple and direct way. [Display omitted] •Sodium ions are successfully inserted into the 1T–2H MoSe2-graphene composite material, which improves the energy storage performance of the material.•The effect of sodium ion insertion on the energy storage performance of MoSe2-graphene composites was discussed in detail through theory and experiments.