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Hierarchical CoSe 2 @NiMn-LDH@Cu 1.8 Se/CF nanosheet arrays with core-shell structure are synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements for green chemistry energy storage. [Display omitted] As an emerging energy storage device, the practical application of supercapacitors (SCs) is currently constrained by their low energy density. Enhancing the capacitance of supercapacitors by leveraging the synergistic effect of multiple components in composite electrodes with well-designed structures can effectively increase their energy density. Here, a wire-sheet-particle hierarchical heterostructured CoSe 2 @NiMn-layered double hydroxide (NiMn-LDH) @Cu 1.8 Se/Copper foam (CF) electrode is synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements. Benefiting from the stable support structure of CuBr 2 , the large specific surface area of NiMn-LDH, and the excellent conductivity of CoSe 2 , the prepared binder-free electrode shows excellent electrochemical properties. The CoSe 2 @NiMn-LDH@Cu 1.8 Se hybrid electrode exhibits a superior specific areal capacitance of 7064 mF cm−2 at 2 mA cm−2 and a stable cyclic performance with 80.11 % capacitance retention after 10,000 cycles. Furthermore, the assembled CoSe 2 @NiMn-LDH@Cu 1.8 Se/CF//AC (activated carbon) asymmetric supercapacitor (ASC) achieves an energy density of 36.6 Wh kg−1 when the power density is 760.6 W Kg−1 and retains 87.35 % of the initial capacitance after 5000 cycles. Overall, this pioneering research provided new insight for preparing supercapacitor electrode materials by selective selenization and ration design of the structures. [ABSTRACT FROM AUTHOR]

CeCoS x -SA/GF porous aerogels are fabricated based on sodium alginate with "egg-box" model and exhibited superior electrochemical properties as well as high mechanical strength. [Display omitted] • CeCoS x -SA/GF aerogels with "egg-box" structure is synthesized. • The CeCoS x -SA/GF electrode exhibits great electrochemical properties. • A portable multifunctional instrument can be powered for 28 mins. • Flexible CeCoS x -SA/GF/KOH/PVA film can be bent and twisted. • The CeCoS x -SA/GF/KOH/PVA film can lift 1 kg plastic bottle. Practical applications of flexible electrochemical energy storage devices are still limited by the lack of robust mechanical structures and high capacitive storage capabilities. Herein, the 3D CeCoS x -SA/GF porous aerogels are designed and prepared based on sodium alginate, which possess a special structure that can be explained by the so-called "egg-box" model. Each metal ion can be paired with the carboxyl and hydroxyl groups of the G monomer on two adjacent sodium alginate molecular chains. Melamine foam is used as carrier for graphene/sodium alginate impregnation and plays an important role on significantly limiting the agglomeration of graphene nanosheets due to their strong π-π stacking. The fabricated electrode based on CeCoS x -SA/GF shows an excellent electrochemical capacitance of 873.3F/g at the current density of 1A/g. In addition, the capacitance retention rate can still remain 87.1 % after 5000 cycles at a high current density of 8 A/g. Moreover, the fabricated all-solid state asymmetric supercapacitor device assembled with CoCeS x -SA/GF and active carbon shows an energy density of 29.58 Wh kg−1 at a power density of 801 W kg−1. For practical applications, the fabricated supercapacitor device can power a multifunctional display for 28 mins and illuminate a small light bulb for 3 mins. Moreover, the KOH/polyvinyl alcohol gel-electrolyte was used to fabricate high-strength and flexible CeCoS x -SA/GF/PVA/KOH composite film electrode, which can be bent at various angles (0°-180°) and can be twisted into various shapes. Notably, the CeCoS x -SA/GF/PVA/KOH composite film can lift plastic bottles containing 500 mL (500 g) and 1000 mL (1 kg) water, respectively, indicating that it has great application potential for wearable and portable electronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] Ortho-hexagonal and highly-oriented NiMnCo-LDH/ZnO@CC self-supporting electrode derived from ZIF-67 covered ZnO nanorod-arrays is fabricated and employed for portable asymmetric solid-state supercapacitor. • Novel ortho -hexagonal NiMnCo-LDH has been synthesized. • ZIF-67 covered ZnO nanorod-arrays as self-supporting electrode is synthesized. • The fabricated electrodes exhibit superior electrochemical properties. • A multifunctional instrument can be powered for more than 30 mins. • The device can be carried outdoors to monitor time, temperature and air humidity. Metal-organic frameworks have attracted much attention due to their abundant redox sites and tunable characteristics, which are advantageous for energy storage applications. However, the low electrical conductivity, poor physical strength and undesirable capacity seriously hinder their applications. Therefore, designing effective and convenient strategies to build composites with unique structures will be of practical significance. Herein, we successfully generate NMC-LDH/ZnO@CC nanocomposites by growing ortho -hexagonal nickel–cobalt layered double hydroxide (NMC-LDH) nanosheets in-situ on ZIF-67 precursor covering vertical arrays of ZnO nanorods. As a result of the unqiue ortho -hexagonal structure, highly ordered arrangement of active substances and multi-dimensional spaces of the prepared NMC-LDH/ZnO@CC binder-free electrode, its capacitance is as high as 9258 mF cm−2 at a current density of 2 mA cm−2 and the capacitance retention is maintained at 87.5 % after 5000 cycles. Furthermore, in order to explore the practical value of the prepared binder-free electrode, the NMC-LDH/ZnO@CC//AC solid-state asymmetric supercapacitor device is assembled. The energy density of the assembled supercapacitor is 24.6 W h kg−1 at a power density of 170 W kg−1 and 1020 W kg−1 at an energy density of 11.8 W h kg−1. In addition, a versatile instrument for monitoring air humidity, time and ambient temperature in portable environments can be powered by a single ultracapacitor unit for more than 30 min. Overall, this study provides a unique strategy for synthesizing ZIF derivatives with novel morphologies for electrochemical energy storage applications. [ABSTRACT FROM AUTHOR]