Hydrogen Bonding-Reinforced Hydrogel Electrolyte for Flexible, Robust, and All-in-One Supercapacitor with Excellent Low-Temperature Tolerance.

Flexible supercapacitors are promising energy storage devices for emerging wearable electronics. However, due to the poor mechanical strength, complicated device manufacturing process, and unsatisfactory low-temperature tolerance, their overall performance for practical applications is hindered. Herein, we report a hydrogen bonding-reinforced, dual-crosslinked poly(vinyl alcohol), acrylic acid, and H2SO4 (PVA-AA-S) hydrogel electrolyte for all-in-one flexible supercapacitors. The PVA-AA-S hydrogel demonstrates excellent compressive/tensile properties and high ionic conductivity. It tolerates compressive stress of 0.53 MPa and is stretchable up to 500%. The hydrogel-based all-in-one supercapacitor shows promising electrochemical performance under various harsh conditions. The device energy density and power density reach up to 14.2 µWh cm-2 and 0.94 mW cm-2, respectively. Furthermore, it retains nearly 80% capacitance after being stored at -35 °C for 23 days. The excellent performance of the hydrogel electrolyte originates from its abundant strong hydrogen bonding between polymer chains and water molecules.

Excellent supercapacitance performance of 3-D mesoporous carbon with large pores from FDU-12 prepared using a microwave method.

Highly ordered and three-dimensional (3-D) mesoporous carbon materials were prepared through a nano-hard templating approach using FDU-12 silica with tunable pore sizes as a template, which was synthesized via a microwave-assisted method. Powder XRD and microscopic techniques such as HR-TEM, HR-SEM, and N2 adsorption-desorption techniques were employed to characterize the structure and textural properties of the prepared mesoporous carbon samples. The characterization results reveal that all the mesoporous carbon samples show a 3-D porous mesostructure with tunable pore diameters (5.7 to 9.4 nm) and a large specific surface area in the range from 451 to 1251 m2 g-1. The supercapacitive behavior of the cubic structured mesoporous carbons was determined using cyclic voltammetry, electrochemical impedance and charge-discharge measurements. The cubic mesoporous carbon materials exhibit a superior capacitive performance with a high specific capacitance value of 315.3 F g-1 at the current density of 1 A g-1, which is much higher than that of hexagonally-ordered mesoporous carbon with large pore diameters, activated carbon, and carbon nanotubes. The materials also show excellent cyclic stability and extremely low resistance. The superior specific capacitance of these materials is attributed to the combination of excellent surface properties such as large specific surface area, large pore volume and uniform pore diameter, spherical morphology, and a 3-D porous system with cage-type pores.

Controlled synthesis of nanocrystalline Li2MnSiO4 particles for high capacity cathode application in lithium-ion batteries.

Monodispersed Li(2)MnSiO(4) nanoparticles are synthesized via a supercritical solvothermal method at 300 °C for 5 min reaction time. The as-synthesized nanoparticles are free from impurities and have 15-20 nm diameter. After coating with conductive polymer, a discharge capacity of 313 mA h g(-1) is obtained for the first time because of nearly 2Li(+) reaction.