Improved chemical precipitation prepared rapidly NiCo2S4 with high specific capacitance for supercapacitors

Facile synthesis of Ni3Se4/Ni0.6Zn0.4O/ZnO nanoparticle as high-performance electrode materials for electrochemical energy storage device

To enhance the performance of transition metal chalcogenide composite electrode material, a key point is a composite design and preparation based on the synergistic effect between the oxide and selenide materials. With a facile 'one step template-annealing' step, Ni₃Se₄, Ni_0.6Zn_0.4O and ZnO are simultaneously synthesized, by 500 °C annealing. With the increase of annealing temperature from 350 °C to 600 °C, nickel selenides change from NiSe₂to Ni₃Se₄to NiSe. The charge storage capacity increases first and then decreases with the increase of annealing temperature, and the 500 °C annealing obtained three compound composite Ni₃Se₄/Ni_0.6Zn_0.4O/ZnO (NNZ-500) nanoparticle material displayed a high specific capacitance of 1089.2 F g^-1at 1 A g^-1, and excellent cycle stability of 99.8% capacitance retention after 2000 cycles at 5 A g^-1. Moreover, an asymmetric supercapacitor was assembled with NNZ-500 as the positive electrode material and activated carbon as the negative electrode material. This kind of asymmetric supercapacitor demonstrated a high energy density of 53.4 Wh kg^-1at 819.0 W kg^-1, and cycle stability with 98.6% capacitance retention after 2000 cycles. This material preparation approach provides great potential for the future development of high performance transition metal composite electrode materials in energy storage applications.

Hollow nanotube arrays of nickle-cobalt metal sulfide for high energy density supercapacitors

High energy density is still difficult to achieve using existing metal sulfides because of their low specific capacitance. To improve capacitance, a series of nickel and cobalt metal sulfides with different Ni/Co ratios were synthesized by a two-step hydrothermal method. Using the combining method of experimental research and first-principles calculation, the morphology, structural stability, electronic structure and electrochemical properties of metal sulfides were investigated systematically. The results show that the morphology of metal sulfides gradually grows from two-dimensional structure to nanotube arrays, and finally to nanorod arrays, as the Ni/Co ratios decrease. Among them, the NC24 sample with the Ni/Co ratio of 1 : 2 is a hollow nanotube array composed of NiCo₂S₄, which shows excellent electrochemical performance. The specific capacity of the NC24 sample reaches 1527C g^-1 at 1 A g^-1, and the capacity retention is 93.81% at 10 A g^-1 after 2000 cycles. Furthermore, a symmetrical supercapacitor assembled from the NiCo₂S₄ nanotube array shows a high energy density of 67.5 W h kg^-1. This strategy develops a nanotube array of metal sulfides and expands its application in a high energy density supercapacitor.

A Magnesium/Lithium Hybrid-Ion Battery with Modified All-Phenyl-Complex-Based Electrolyte Displaying Ultralong Cycle Life and Ultrahigh Energy Density

Magnesium/lithium hybrid-ion batteries (MLHBs) combine the advantages of high safety and fast ionic kinetics, which enable them to be promising emerging energy-storage systems. Here, a high-performance MLHB using a modified all-phenyl complex with a lithium bis(trifluoromethanesulfonyl)imide electrolyte and a NiCo₂S₄ cathode on a copper current collector is developed. A reversible conversion involving a copper collector with NiCo₂S₄ efficiently avoids the electrolyte dissociation and diffusion difficulties of Mg²⁺ ions, enabling low polarization and fast redox, which is verified by X-ray absorption near edge structure analysis. Such combination affords the best MLHB among all those ever reported, with a reversible capacity of 204.7 mAh g^-1 after 2600 cycles at 2.0 A g^-1, and delivers an ultrahigh full electrode-basis energy density of 708 Wh kg^-1. The developed MLHB also achieves good rate performance and temperature tolerance at -10 and 50 °C with a low electrolyte consumption. The hybrid-ion battery system presented here could inspire a broad set of engineering potentials for high-safety battery technologies and beyond.