In this work, a facile hydrothermal approach for the shape-controlled synthesis of NiCo2S4 architectures is reported. Four different morphologies, urchin-, tube-, flower-, and cubic-like NiCo2S4 microstructures, have been successfully synthesized by employing various solvents. The obtained precursors and products have been characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. It is revealed that the supersaturation of nucleation and crystal growth is determined by the solvent polarity and solubility, which can precisely control the morphology of NiCo2S4 microstructures. The detailed electrochemical performances of the various NiCo2S4 microstructures are investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The results indicate that the tube-like NiCo2S4 exhibits promising capacitive properties with high capacitance and excellent retention. Its specific capacitance can reach 1048 F g(-1) at the current density of 3.0 A g(-1) and 75.9% of its initial capacitance is maintained at the current density of 10.0 A g(-1) after 5000 charge-discharge cycles.

Using a simple hydrothermal route coupled with a carbonization treatment, one-dimensional NiCo 2 S 4 @MnO 2 heterostructures have been fabricated successfully.Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) measurements showed that MnO 2 nanoflakes uniformly wrapped on the surface of NiCo 2 S 4 nanotube and formed core-shell heterostructured nanotubes, which combine both advantages of NiCo 2 S 4 such as excellent cycle stability and MnO 2 with high capacity. Serving as supercapacitor electrode, the NiCo 2 S 4 @MnO 2 heterostructures give a remarkable specific capacitance (1337.8 F/g at the current density of 2.0 A/g) and excellent cycling stability (remaining 82% after 2000 cycles) due to their synergistic effects of NiCo 2 S 4 and MnO 2 . Such unique nanoarchitectures demonstrate potential applications in energy storage electrodes and inspire researchers continue to focus on heterostructured materials.

To meet the requirements of the rapid development of large-scale energy storage systems, "Beyond Li-ion battery (LIB)" systems are attracting more and more attention. [1][2][3][4][5] Among various alkali metals ion batteries, potassium-ion batteries (KIBs) exhibit many advantages for large-scale energy storage system applications including: [6,7] 1) the low manufacturing costs because of the natural abundance of their raw materials; 2) much lower redox potential of K/K + (−2.93 V vs standard hydrogen electrode) leading to higher open-circuit voltage and higher energy density compared with sodiumion batteries (SIBs). [8][9][10] According to the advantages and properties of low production costs and high energy density, the KIB is considered as a promising energy storage system for large-scale energy storage application. However, KIBs suffer from inferior cyclic stability and insufficient power density resulting from the structure collapse of electrode materials due to the bigger K + Constructing 2D heterostructure materials by stacking different 2D materials can combine the merits of the individual building blocks while eliminating their shortcomings. Dichalcogenides are attractive anodes for potassium-ion batteries (KIBs) due to their high theoretical capacity. However, the practical application of dichalcogenide is greatly hampered by the poor electrochemical performance due to sluggish kinetics of K + insertion and the electrode structure collapse resulting from the large K + insertion. Herein, heterostructures of 2D molybdenum dichalcogenide on 2D nitrogen-doped carbon (MoS 2 , MoSe 2 -on-NC) are prepared to boost their potassium storage performance. The unique 2D heterostructures possess built-in heterointerfaces, facilitating K + diffusion. The robust chemical bonds (CS, CSe, CMo bonds) enhance the mechanical strength of electrodes, thus suppressing the volume expansion. The 2D N-doped carbon nanosheets interconnected as a 3D structure offer a fast diffusion path for electrons. Benefitting from these merits, both the MoS 2 -on-NC and the MoSe 2 -on-NC exhibit unprecedented cycle life. Moreover, the electrochemical reaction mechanism of MoSe 2 is revealed during the process of potassiation and depotassiation.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.