Rational design of hierarchical Ni-Mo bimetallic Selenide/N-doped carbon microspheres toward high–performance potassium ion batteries

Hierarchical Ni–Mo bimetallic selenide/N-doped carbon microspheres (NMSe/NC) are successfully synthesized as anodes for potassium ion batteries (KIBs) via a facile strategy. The obtained microspheres consisted of primary 2D building blocks; this unique structure provides sufficient reaction sites and increases the contact area with the electrolyte. Furthermore, the synergistic effect between different metallic ions and the conductive carbon matrix can enhance the electrochemical properties of the composites. Accordingly, the NMSe/NC microspheres exhibited remarkable K-ion storage performance as anode materials for KIBs. • Hierarchical NiSe 2 -MoSe 2 /NC microsphere is prepared by a simple strategy. • The synergetic effect by Ni and Mo species promotes reaction kinetics. • Charge/discharge process of multicomponent with K + ions is investigated. • NMSe/NC composite shows excellent K-ion storage performance. Potassium ion batteries (KIBs) have received a lot of attention in large-scale energy storage applications because of abundant potassium resources. However, owing to the poor structural durability of electrode materials and sluggish reaction kinetics, the commercialization of KIBs is challenging. Herein, we design a hierarchically structured Ni–Mo bimetallic selenide/N-doped carbon microsphere (NMSe/NC) as an advanced anode material for KIBs. The hierarchical Ni-Mo/polydopamine microsphere precursor, obtained from the spontaneous chemical reaction of NiMoO 4 nanorods with dopamine hydrochloride, is converted into heterostructured-Ni–Mo selenide crystals confined in a hierarchical NC matrix via a two-step thermal treatment. The unique hierarchical surface structure and the synergistic effect of Mo and Ni species provide sufficient electrochemical reaction sites and promote the reaction kinetics. Furthermore, the proximate contact between the active materials and the N-doped carbon matrix can facilitate electron transportation and enhance the structural robustness of the electrode. Consequently, the resulting NMSe/NC hierarchical microspheres delivered a high reversible capacity of 332 mA h g −1 after 200 cycles (current density: 0.5 A g −1 ) and a remarkable rate capability of 206 mA h g −1 (current density: 2.0 A g −1 ). The excellent electrochemical performance of NMSe/NC indicates their potential for KIB commercialization in large-scale energy storage systems in the future.