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[Display omitted] Two dimensional (2D) materials, with ideal interlayer spacing for ion intercalation/de-intercalation, are quite appealing for hybrid supercapacitors (HSCs) in the pursuit of harvesting promising electrochemical performance. Integrating different 2D materials together is one effective strategy to achieve such goals. However, preserving the ion diffusion channel and accelerating electron transfer should be considered during the compositing process. Herein, we propose a two-step strategy to efficiently composite cobalt hydroxide (Co(OH) 2) and Ni-based MOF (Ni-MOF-24), in which a vertically oriented Ni-MOF@Co(OH) 2 array on nickel foam is obtained. The maximum specific capacitance of 1448 Fg−1 (2 Ag−1) is delivered by Ni-MOF@Co(OH) 2. Accordingly, a hybrid Ni-MOF@Co(OH) 2 //AC HSC is thereof assembled, which outputsa high specific power of 22,400 W kg−1 and a considerable specific energy of 45.7 Wh kg−1. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) are expected to be promising pseudocapacitve materials because of their potential redox sites and porous structures. Nevertheless, the conductivity inferiority of MOF strongly decreases their structural advantages, therefore resulting in unsatisfying electrochemical performance. Herein, we propose an efficient strategy to enhance conductivity and thus electrochemical properties, in Ni(OH)2 is electrochemically deposited on carbon nanowalls as the precursor for oriented MOF. The synthesized vertically oriented MOF sheets show an almost triple high capacitance of 677 F g−1 than MOF powder of 239 F g−1 at the current density of 2 A g−1. Correspondingly, an asymmetric supercapacitor is fabricated, which can deliver a maximum energy density of 20.7 Wh kg−1 and a maximum power density of 23 200 W kg−1. These promising results indicate that modulating the conductivity of MOF is the key step to pursuit upgrading electrochemical performance. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) with numerous potential pseudocapacitive sites are quite appealing to supercapacitors with high specific and areal capacitances. However, MOFs suffer from a low conductivity nature, resulting in a mediocre electrochemical performance. Herein, we propose a template-growth strategy of MOF to enhance both specific and areal capacitances of MOF as the electrode material for supercapacitor. As the loading mass of MOF increases from 2 to 5 mg, the specific capacitance also increases from 937 to 2387 Fg−1 (431 to 1098 Cg−1) and areal capacitance 1.87 to 11.94 Fcm−2 (0.86 to 5.49 Ccm−1). Accordingly, a hybrid MOF//AC supercapacitor can deliver a maximum energy density of 67 Wh kg−1 and a maximum power density of 6000 W kg−1. These results point to a way to fabricate MOF electrode of supercapacitor with high specific and areal capacitance, which leads them to a more practical future. [ABSTRACT FROM AUTHOR]

Abstract: Cobalt hydroxide (Co(OH)2) is a promising electrode material for hybrid devices because of its intrinsic battery‐mimic mechanism for energy storage. However, conventional electrolytes suitable for Co(OH)2 will lead to performance failure in a harsh environment, which hinders its industrial application at ambient temperature. Here, we propose an anti‐freezing aqueous electrolyte composed of NaOH and a high concentration of NaClO4 for Co(OH)2 electrode, which can still fully function at −30 °C. At this temperature, the energy density of a Co(OH)2–active carbon hybrid capacitor can reach 16.52 Wh kg−1, which has a 72 % energy‐density retention at 20 °C. The hybrid capacitor shows excellent cyclability with the anti‐freezing electrolyte at −30 °C, presenting only 3.5 % drop of the capacitance after 500 cycles. This designed anti‐freezing electrolyte may put more pseudocapacitive materials into more practical use, particularly in northern harsh climates. [ABSTRACT FROM AUTHOR]

Abstract: Metal organic frameworks (MOFs) are considered as promising candidates for supercapacitors because of high specific area and potential redox sites. However, their shuffled orientations and low conductivity nature lead to severely‐degraded performance. Designing an accessibly‐manipulated and efficient method to address those issues is of outmost significance for MOF application in supercapacitors. It is the common way that MOFs scarify themselves as templates or precursors to prepare target products. But to reversely think it, using target products to prepare MOF could be the way to unlock the bottleneck of MOFs' performance in supercapacitors. Herein, a novel strategy using Co(OH)2 as both the template and precursor to fabricate vertically‐oriented MOF electrode is proposed. The electrode shows a double high specific capacitance of 1044 Fg−1 and excellent rate capability compared to MOF in powder form. An asymmetric supercapacitor was also fabricated, which delivers a maximum energy density of 28.5 W h kg−1 at a power density of 1500 W kg−1, and the maximum of 24000 W kg−1 can be obtained with a remaining energy density of 13.3 W h kg−1. Therefore, the proposed strategy paves the way to unlock the inherent advantages of MOFs and also inspires for advanced MOF synthesis with optimum performance. [ABSTRACT FROM AUTHOR]

The conventional enhancement in capacitive performance that only relies on electrode materials is limited. Here, based on the system-level design principle, we explore the possibility of enhancing capacitance through both electrode and electrolyte. A novel and ultrahigh-performance asymmetric supercapacitor has been fabricated using two redox electrode systems. The positive electrode system consists of graphene supported Co(OH) 2 nanosheet (Co(OH) 2 /GNS) electrode and mixed KOH and K 3 Fe(CN) 6 aqueous electrolyte. And the negative electrode system comprises carbon fiber paper supported activated carbon (AC/CFP) electrode in mixed KOH and p-phenylenediamine (PPD) aqueous electrolyte. The novel asymmetric supercapacitor exhibits a significantly improved capacitive performance (specific capacitance of 204.5 Fg −1 , operational voltage of 2.0 V) in comparison with that of the conventional asymmetric supercapacitor (66.8 Fg −1 , 1.5 V) fabricated without redox electrolyte. The improvement is attributed high reversibility and conductivity of electrode materials and redox electrolyte, as well as the synergistic effect between the two electrode systems, resulting in a ultrahigh energy density (114.5 Whkg −1 at a power density of 1000 Wkg −1 ), excellent power density (4000 Wkg −1 at an energy density of 31.6 Whkg −1 ) and long-term cycling stability (after 20000 cycles, initial capacitance remains well). These encouraging results afford a facile and efficient way to fabricate ultrahigh-performance supercapacitors for the increasing demands on the energy storage devices. [ABSTRACT FROM AUTHOR]