Constructing hierarchical core‐shell configuration from well‐known metal sulfides is one way to further tune and utilize unique species. Herein, a novel core‐shell structure is developed based on CoS deposited on NiS nanosheets, which involves hydrothermal and electrodeposition method. The micromorphology of the composite electrode can be optimized by adjusting the cycles of electrodeposition. Taking advantages of the highly conductive, open framework of the core‐shell nanolayer, the 5‐NiS@CoS electrode shows a specific capacitance of 1210 F g−1 at a current density of 1 A g−1 (retaining 82% from 1 to 10 A g−1, while NiS substrate is only 39%). The specific capacitance retention rate is 80.94% at 10 A g−1 after 2000 cycles (NiS substrate is 59.6%). Moreover, NiS@CoS//AC asymmetric supercapacitor device delivers an energy density of 24.1 Wh kg−1 at a power density of 752.15 W kg−1 and remarkable stability (over 80% retention after 5000 cycles). This work may prompt the exploration of the synthesis of inexpensive compounds incorporating highly reactive components for supercapacitors.

No abstract

No abstract

Functionalized carbon nanomaterials are potential candidates as anode materials in potassium-ion batteries (PIBs). The inevitable defect sites in architectures greatly affect the physicochemical properties of carbon nanomaterials, thus defect engineering...

No abstract

No abstract

Design and fabrication of novel electrode materials with excellent specific capacitance and cycle stability are urgent for advanced energy storage devices, and the combinability of multiple modification methods is still insufficient. Herein, Ni 2+ , Zn 2+ double-cation-substitution Co carbonate hydroxide (NiZnCo-CH) nanosheets arrays were established on 3D copper with controllable morphology (3DCu@NiZnCo-CH). The selfstanding scalable dendritic copper offers a large surface area and promotes fast electron transport. The 3DCu@NiZnCo-CH electrode shows a markedly improved electrochemical performance with a high specific capacity of ∼1008 C g −1 at 1 A g −1 (3.2, 2.83, and 1.26 times larger than Co-CH, ZnCo-CH, and NiCo-CH, respectively) and outstanding rate capability (828.8 C g −1 at 20 A g −1 ) due to its compositional and structural advantages. Density functional theory (DFT) calculation results illustrate that cation doping adjusts the adsorption process and optimizes the charge transfer kinetics. Moreover, an aqueous hybrid supercapacitor based on 3DCu@NiZnCo-CH and rGO demonstrates a high energy density of 42.29 Wh kg −1 at a power density of 376.37 W kg −1 , along with superior cycling performance (retained 86.7% of the initial specific capacitance after 10,000 cycles). Impressively, these optimized 3DCu@NiZnCo-CH//rGO devices with ionic liquid can be operated stably in a large potential range of 4 V with greatly enhanced energy density and power capability (110.12 Wh kg −1 at a power density of 71.69 W kg −1 ). These findings may shed some light on the rational design of transition-metal compounds with tunable architectures by multiple modification methods for efficient energy storage.

A fluoride-ion battery (FIB) is a novel type of energy storage system that has a higher volumetric energy density and low cost. However, the high working temperature (>150 °C) and unsatisfactory cycling performance of cathode materials are not favorable for their practical application. Herein, fluoride ion-intercalated CoFe layered double hydroxide (LDH) (CoFe-F LDH) was prepared by a facile co-precipitation approach combined with ion-exchange. The CoFe-F LDH shows a reversible capacity of ∼50 mAh g–1 after 100 cycles at room temperature. Although there is still a big gap between FIBs and lithium-ion batteries, the CoFe-F LDH is superior to most cathode materials for FIBs. Another important advantage of CoFe-F LDH FIBs is that they can work at room temperature, which has been rarely achieved in previous reports. The superior performance stems from the unique topochemical transformation property and small volume change (∼0.82%) of LDH in electrochemical cycles. Such a tiny volume change makes LDH a zero-strain cathode material for FIBs. The 2D diffusion pathways and weak interaction between fluoride ions and host layers facilitate the de/intercalation of fluoride ions, accompanied by the chemical state changes of Co2+/Co3+ and Fe2+/Fe3+ couples. First-principles calculations also reveal a low F– diffusion barrier during the cyclic process. These findings expand the application field of LDH materials and propose a novel avenue for the designs of cathode materials toward room-temperature FIBs.