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DFT calculation is used to study the electrochemical capacity enhancement mechanism of the fabricated flexible 3D porous rOHNM-AGs electrodes based on open-hollow Ni-MOF microspheres with high mechanical strength and superior electrochemical properties. [Display omitted] • 3D rOHNM-AGs are achieved by embedding open-hollow Ni-MOF microspheres into graphene nanosheets. • DFT calculation reveals charge-transfer interaction between the rOHNM-AGs and OH– ions. • The rOHNM-AGs/KOH/PVA film can be twisted with different angles, which can lift 500 g plastic bottle. • The fabricated rOHNM-AGs electrode exhibit superb specific capacitance of 1644F·g−1 at 1 A·g−1. • A portable multifunctional instrument can be powered by all-solid-state supercapacitor device for 15 mins. Metal-organic frameworks (MOFs) are extensively used for electrode materials of supercapacitors under their unique characteristics like customizable pore size, plentiful active sites and tunable structure. However, the MOFs lack adequate electrical conductivity and satisfactory stability, when directly applied to supercapacitor electrode materials, limiting the further improvement of their electrochemical properties. Accordingly, three-dimensional porous aerogels (rOHNM-AGs) have been achieved by embedding open-hollow nickel-based metal–organic framework microspheres between graphene layers. Under the controllable and highly ordered metal nodes as well as organic linkers, the prepared rOHNM-AGs still reserve the preponderance of MOF materials with multifarious exceptional constituent and configurational benefits. Furthermore, the remarkable electrical conductivity from graphene leads to a significant increase in electron/ion transport rate. In addition, charge-transfer interaction between the acceptor of OH– ions and the donor of rOHNM-AGs has been exposed by the density functional theory calculations. Moreover, a pliable and high tensile rOHNM-AGs/PVA/KOH film electrode has been fabricated by the PVA/KOH gel-electrolyte, which is capable of curving at multifarious angles. For actual utilizations, the manufactured supercapacitor apparatus can run a multi-purpose display for over 15 mins. Therefore, this groundbreaking research furnishes a new inspiration for preparing composite electrodes based on MOFs and graphene for flexible asymmetric supercapacitors. [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]

[Display omitted] • Porous NCS nanosheets are prepared by a one-step method. • CS@NCS/CC core–shell hetero-nanostructure with abundant mesopores is constructed. • Flexible CS@NCS/CC electrode can be bent and twisted at multiple angles. • CS@NCS/CC electrode exhibits excellent electrochemical performance. • CS@NCS/CC//AC/CC device continuously lights up a small bulb for 12 min. Flexible portable supercapacitor devices have gained increasing attention in the field of energy storage in recent years. However, challenges remain in the selection of applicable flexible materials and/or the preparation of materials. Through our research, we have effectively constructed a flexible CS@NCS/CC core–shell hetero-nanostructured cathode material by anchoring Co 9 S 8 (CS) nanopins on a flexible carbon cloth (CC) substrate firstly, and then wrapping NiCo 2 S 4 (NCS) nanosheets on the outer surface of CS nanopins. In this process, we have improved the traditional two-step method of preparing NCS nanosheets into a one-step method, which has greatly improved the efficiency of the material preparation. The prepared CS@NCS/CC material has abundant mesopores, stable core–shell heterostructures and multiple valence states of metal ions, which enable the CS@NCS/CC electrode material to have strong electrochemical reaction kinetics and excellent cycling stability. Additionally, the CC as the flexible substrate improves the charge transfer capability of the transition metal composite. Benefiting from the synergistic effect of these favorable factors, the electrode material exhibits a high C s value of 2020.6F g−1, which maintains 89.8% after 10,000 constant current charges and discharges. It is worth noting that the CS@NCS/CC can be folded and twisted at multiple angles, which proves that it can be used in wearable applications. The flexible hybrid supercapacitor CS@NCS/CC//AC/CC displays terrific energy density (58 Wh kg−1, at 800 W kg−1) with the synergistic effect of pseudocapacitance and electrical double-layer capacitance, and a capacitance retention rate of 92.9% after 10,000 cycles of constant current charging and discharging. Therefore, using CC as the flexible substrate and transition metal sulphides as the active material is an effective strategy for constructing high-performance flexible supercapacitors. [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]