Electrochemical energy storage devices (EESDs) have caused widespread concern, ascribed to the increasing depletion of traditional fossil energy and environmental pollution. In recent years, nickel cobalt bimetallic sulfides have been regarded as the most attractive electrode materials for super-performance EESDs due to their relatively low cost and multiple electrochemical reaction sites. In this work, NiCo-bimetallic sulfide NixCo3−xS4particles were synthesized in a mixed solvent system with different proportion of Ni and Co salts added. In order to improve the electrochemical performance of optimized Ni2.5Co0.5S4electrode, the Ni2.5Co0.5S4particles were annealed at 350 °C for 60 min (denoted as Ni2.5Co0.5S4-350), and the capacity and rate performance of Ni2.5Co0.5S4-350 was greatly improved. An aqueous NiCo-Zn battery was assembled by utilizing Ni2.5Co0.5S4-350 pressed onto Ni form as cathode and commercial Zn sheet as anode. The NiCo-Zn battery based on Ni2.5Co0.5S4-350 cathode electrode delivers a high specific capacity of 232 mAh g−1at 1 A g−1and satisfactory cycling performance (65% capacity retention after 1000 repeated cycles at 8 A g−1). The as-assembled NiCo-Zn battery deliver a high specific energy of 394.6 Wh kg−1and long-term cycling ability. The results suggest that Ni2.5Co0.5S4-350 electrode has possible applications in the field of alkaline aqueous rechargeable electrochemical energy storage devices for supercapacitor and NiCo-Zn battery.Keywords:NixCo3−xS4structures;micro/nanostructures;supercapacitors;Ni-Zn batteries
Many researches are devoted to design the wearable fibrous energy storage devices with miniaturization in order to satisfy the large demand of power for portable wearable electronics. As a kind of flexible battery, one-dimensional yarn-like nickel-zinc (Ni-Zn) battery has a lot of disadvantages such as low energy density and poor power density. Significantly, metal–organic framework (MOF) material provides an opportunity to solve the preceding shortcomings due to its porous structure, excellent specific surface area and multi-functionalization. In this study, the nickel cobalt layered double hydroxides (NiCo LDHs) with triangular micro sheet array and nano sheet structure is designed and prepared on silver coated nylon fibers (SCNF) as the flexibly fibrous Ni-Zn battery cathodes (SCNF@Ni@MOF@NiCo LDHs yarn electrode), which have high specific surface area and super structure stability even during bending of the yarn. Therefore, the cathodes have abundant active sites, excellent electron conduction and fast ion diffusion. The assembled aqueous Ni-Zn battery is featured with suitable capacitance (342 mAh/g at 7.6 A/g), appropriate energy density (572.5 Wh/g at 2.59 W g −1 ) and superior stability (55 % after 5000 cycles). In addition, the obtained one-dimensional yarn-like Ni-Zn battery has excellent flexibility and high capacity retention (90 % after 1000 bends and over 80 % after different deformation ways such as bend, squeeze and twist). These fascinating results demonstrate that the SCNF@Ni@MOF@NiCo LDHs yarn electrode have great application potential in wearable energy storage devices.
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