Ni–Co coordination hollow spheres for high performance flexible all-solid-state supercapacitor

One-Step Solvothermal Synthesis of Raspberry-like NiCo-MOF for High-Performance Flexible Supercapacitors for a Wide Operation Temperature Range

As a novel electrode material for energy storage, metal-organic frameworks (MOFs) emerge with plenty of merits and certain drawbacks in the field of supercapacitors. Nevertheless, most MOFs synthesized for the moment are faced with dimension/distribution issues and dissatisfactory electrical conductivity. Hence, in this paper, NiCo-MOF was successfully fabricated by applying a one-step solvothermal method, from which NiCo-MOF-3 presents an optimal electrochemical performance compared to other NiCo-MOFs and Ni/Co-MOF. Owing to its unique three-dimensional spherical raspberry structure, NiCo-MOF-3 demonstrates an available internal resistance and electron transfer resistance to ameliorate electrical energy storage, exhibiting an excellent mass specific capacitance of 639.8 F/g at 1 A/g. Then, a flexible quasi-solid-state asymmetric supercapacitor was assembled with NiCo-MOF-3 as the positive electrode. The introduction of K₃[Fe(CN)₆] and glycerin in the gel electrolyte facilitates the maximum energy density of 66.3 Wh/kg of the device, with a corresponding power density reaching its maximum of 12,047 W/kg. The device's apparent energy density, excellent flexibility, and temperature resistance reveal that our method to prepare supercapacitor electrode material possesses more advantages than those in the former literature.

Metal-Organic Framework Materials for Electrochemical Supercapacitors

Exploring new materials with high stability and capacity is full of challenges in sustainable energy conversion and storage systems. Metal-organic frameworks (MOFs), as a new type of porous material, show the advantages of large specific surface area, high porosity, low density, and adjustable pore size, exhibiting a broad application prospect in the field of electrocatalytic reactions, batteries, particularly in the field of supercapacitors. This comprehensive review outlines the recent progress in synthetic methods and electrochemical performances of MOF materials, as well as their applications in supercapacitors. Additionally, the superiorities of MOFs-related materials are highlighted, while major challenges or opportunities for future research on them for electrochemical supercapacitors have been discussed and displayed, along with extensive experimental experiences.

Preparation of Y-Doped La2Ti2O7 Flexible Self-Supporting Films and Their Application in High-Performance Flexible All-Solid-State Supercapacitor Devices

Flexible all-solid-state supercapacitors have drawn more attention owing to the rapid growth of wearable electronic equipments. Herein, we have succeeded in synthesizing a series of Y-doped lanthanum titanate flexible self-supporting films (LSF-x, 0.1 ≤ x ≤ 0.5) and investigating the change of microstructures, morphological characteristics, and lattice structures of these films affected by different Y-doping contents. To further determine the optimum Y-doping content, we have explored the electrochemical properties of working electrodes prepared by LSF-x (0.1 ≤ x ≤ 0.5) samples as the main active material. As the LSF-0.2 electrode has the best areal capacitance of 1.3 F·cm-2 at 2 mA·cm-2, we use the LSF-0.2 electrodes and PVA-Na2SO4 gel to fabricate a flexible all-solid-state supercapacitor device. This device has a high areal capacitance of 255.9 mF·cm-2 at a current density of 2 mA·cm-2 with a high cell voltage of 2.1 V, while the corresponding energy density is 156.8 μWh·cm-2 with a power density of 2.1 mW·cm-2. Moreover, it also shows a long cycling life and outstanding flexibility. Therefore, the LSF-0.2 sample can be used as an excellent energy-storage material for a wearable electronic device.