decreases the cost because it eliminates the necessity of having an inert atmosphere or using organic solvents. Thus, Zn-based energy storage systems such as Zn-ion, [5,6] Zn-alkali, [2,7] Zn-flow, [8] Zn-I 2 , [9] Zn-air, [10] and Zn-ion capacitors [11,12] have received attention because of their practicality and good performance. The easy and scalable production of Zn electrodes is crucial for securing the continued development of improved Zn-based battery systems, but recent research has highlighted the problem of dendrite formation caused by non-uniform charge distribution and side reactions (hydrogen evolution, Zn corrosion) during plating and stripping which causes severe deterioration of Zn batteries, and significantly limits their efficiency and life. Because of dendrite growth, such devices suffer from a short cycle life, capacity fade, and a high possibility of internal short circuit formation and safety problems. Dendrite growth is not only a challenging problem for Zn batteries but is also a problem for Li-metal batteries, and suppression of dendrite formation in anodes is a great challenge for battery research. [13] Although there is a considerable effort to suppress dendrite formation, it still remains the most crucial problem for batteries. To overcome this problem, several strategies have been used, that is, redesigning the anode, [2,14] composite formation or anode surface modifications, [15] reformulating electrolytes with additives, and the use of solid-state electrolytes. [3,16,17] Uniform charge distribution on the anode surface is essential for eliminating this problem.ZIF-8, one of the zeolitic imidazole frameworks (a subgroup of the metal-organic frameworks [MOFs]), has a Zn-coordinated crystal structure and high microporosity. [12,18] The use of ZIF-8-derived carbon nanoparticles as a host for electrodeposited Zn has been reported in the literature. [9] We reasoned that a monolithic (conformal) ZIF-8 layer that is directly grown on Zn metal might be a unique strategy to ensure a uniform charge and ion distribution at the anode-electrolyte interface. MOF-integrated Zn anodes might facilitate reversible Zn plating and stripping cycles, and prevent dendrite formation and side reactions. It is also possible that pyrolyzed MOF-integrated Zn anodes might have a similar mechanism and electrochemical properties due to their N-content, porosity, and hydrophilicity.Here, we report the design and construction of novel MOFbased Zn anodes to achieve the above-mentioned goals for Znbased energy storage systems. The surface of a bare Zn foil was selectively oxidized and MOFs were directly grown on it by a wet chemistry method. The resulting anodes were used Zinc-based batteries have a high capacity and are safe, cost-effective, environmentally-friendly, and capable of scalable production. However, dendrite formation and poor reversibility hinder their performance. Metal-organic framework (MOF)-based Zn anodes are made by wet chemistry to address these issues. These MOF-based anodes exhibit high effi...
We describe a simple process for the fabrication of transparent and flexible, solid-state supercapacitors. Symmetric electrodes made up of binder-free single walled carbon nanotube (SWCNT) thin films were deposited onto polydimethylsiloxane substrates by vacuum filtration followed by a stamping method, and solid-state supercapacitor devices were assembled using a gel electrolyte. An optical transmittance of 82% was found for 0.02 mg of SWCNTs, and a specific capacitance of 22.2 F/g was obtained. The power density can reach to 41.5 kW•kg −1 and shows good capacity retention (94%) upon cycling over 500 times. Fabricated supercapacitors will be relevant for the realization of transparent and flexible devices with energy storage capabilities, displays and touch screens in particular.
The synthesis of a new type of redox‐active covalent triazine framework (rCTF) material, which is promising as an anode for Li‐ion batteries, is reported. After activation, it has a capacity up to ≈1190 mAh g−1 at 0.5C with a current density of 300 mA g−1 and a high cycling stability of over 1000 discharge/charge cycles with a stable Coulombic efficiency in an rCTF/Li half‐cell. This rCTF has a high rate performance, and at a charging rate of 20C with a current density of 12 A g−1 and it functions well for over 1000 discharge/charge cycles with a reversible capacity of over 500 mAh g−1. By electrochemical analysis and theoretical calculations, it is found that its lithium‐storage mechanism involves multi‐electron redox‐reactions at anthraquinone, triazine, and benzene rings by the accommodation of Li. The structural features and progressively increased structural disorder of the rCTF increase the kinetics of infiltration and significantly shortens the activation period, yielding fast‐charging Li‐ion half and full cells even at a high capacity loading.
This review focuses on the silver nanowires (Ag NWs) based stretchable and flexible energy devices for self-sustainable devices.
The design and synthesis of a necklace‐like nitrogen‐doped tubular carbon (NTC) are presented by growing microporous polyhedral ZIF‐8 particles and a uniform layer of ZIF‐8 on sacrificial ZnO tetrapods (ZTPs). Oxygen vacancies together with defect regions on the surface of the ZTPs result in the formation of ZIF‐8 polyhedra in conjunction with a very thin shell. This necklace‐like NTC structure has a high N content, very large surface area, ultrahigh microporosity, and quite high electrical conductivity. NTC‐based symmetrical supercapacitor and zinc‐ion capacitor (ZIC) devices are fabricated and their electrochemical performance is measured. The NTC supercapacitor shows an ultrahigh rate capability (up to 2000 mV s−1) and promising cycle life, retaining 91.5% of its initial performance after 50 000 galvanostatic charge–discharge cycles. An aqueous ZIC, constructed using the NTC, has a specific capacitance of 341.2 F g−1 at a current density of 0.1 A g−1 and an energy density of 189.6 Wh kg−1 with a 2.0‐V voltage window, respectively. The outstanding performance is attributed to the NTC high N‐doping content, a continuous “polyhedral 3D hollow” architecture and the highly porous microtubular arms exhibiting very high surface area.
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