A poly(vinylphosphonic acid) (PVPA)−(NH.sub.4).sub.2MoO.sub.4), gel polymer electrolyte can be prepared by incorporating redox-mediated Mo, or similar metal, into a PVPA, or similar polymer, matrix. Gel polymer electrolytes including PVPA/MoX, x representing the percent fraction Mo in PVPA, can be used to make supercapacitors including active carbon electrodes. The electrolytes can be in gel form, bendable and stretchable in a device. Devices including this gel electrolyte can have a specific capacitance (Cs) of 1276 F/g, i.e., a more than 50-fold increase relative to a PVPA system without Mo. A PVPA/Mo10 supercapacitor can have an energy density of 180.2 Wh/kg at power density of 500 W/kg, and devices with this hydrogel structure may maintain 85+% of their initial capacitance performance after 2300 charge-discharge cycles.

The present invention provides a high output voltage supercapacitor having a cathode including layers of phosphorene, an anode comprising zinc, and an organic-solvent-based electrolyte including zinc. The supercapacitor demonstrates a high anti-self-discharge. The organic electrolyte may include an anhydrous zinc salt, tetraethylammonium tetrafluoroborate, and propylene carbonate (Et.sub.4NBF.sub.4/PC). The electrochemical stability window of Et.sub.4NBF.sub.4/PC extends beyond 2.5 V. The supercapacitor can be charged to 2.5 V and possesses high initial discharge voltage. The supercapacitor delivered 130 F g.sup.−1 even after more than 9500 cycles at a current density of 0.5 A g.sup.−1. More importantly, the supercapacitor exhibits a capacitance retention of 70.16% even after 500 hours self-discharge behavior.

A nanocomposite electrode and a method of making the nanocomposite. The nanocomposite electrode includes an electrode substrate, nitrogen-doped molybdenum carbide nanosheets, at least one electrolyte, at least one binding compound, and at least one conductive additive. The electrode substrate is coated with a mixture of the nitrogen-doped molybdenum carbide nanosheets, at least one binding compound, at least one conductive additive, and at least one electrolyte, where the electrolyte penetrates the pores of the nitrogen-doped molybdenum carbide nanosheets, and where the nitrogen-doped molybdenum carbide nanosheets are an outer layer of the electrode.

Provided herein are energy storage devices comprising a first electrode comprising a layered double hydroxide, a conductive scaffold, and a first current collector; a second electrode comprising a hydroxide and a second current collector; a separator; and an electrolyte. In some embodiments, the specific combination of device chemistry, active materials, and electrolytes described herein form storage devices that operate at high voltage and exhibit the capacity of a battery and the power performance of supercapacitors in one device.

Provided herein are energy storage devices comprising a first electrode comprising a layered double hydroxide, a conductive scaffold, and a first current collector; a second electrode comprising a hydroxide and a second current collector; a separator; and an electrolyte. In some embodiments, the specific combination of device chemistry, active materials, and electrolytes described herein form storage devices that operate at high voltage and exhibit the capacity of a battery and the power performance of supercapacitors in one device.

An aqueous electrolyte for a pseudo-capacitor and a pseudo-capacitor comprising the same, and more particularly an aqueous electrolyte for a pseudo-capacitor comprising an aqueous solvent, and a certain concentration or more of a lithium salt and a zwitterionic compounds, and a pseudo-capacitor comprising the aqueous electrolyte described above.

The disclosed technology generally relates to energy storage devices, and more particularly to energy storage devices comprising frustules. According to an aspect, a supercapacitor comprises a pair of electrodes and an electrolyte, wherein at least one of the electrodes comprises a plurality of frustules having formed thereon a surface active material. The surface active material can include nanostructures. The surface active material can include one or more of a zinc oxide, a manganese oxide and a carbon nanotube.

Disclosed is a hybrid electrochemical cell with a first conductor having at least one portion that is both a first capacitor electrode and a first battery electrode. The hybrid electrochemical cell further includes a second conductor having at least one portion that is a second capacitor electrode and at least one other portion that is a second battery electrode. An electrolyte is in contact with both the first conductor and the second conductor. In some embodiments, the hybrid electrochemical cell further includes a separator between the first conductor and the second conductor to prevent physical contact between the first conductor and the second conductor, while facilitating ion transport between the first conductor and the second conductor.

Disclosed is a hybrid electrochemical cell with a first conductor having at least one portion that is both a first capacitor electrode and a first battery electrode. The hybrid electrochemical cell further includes a second conductor having at least one portion that is a second capacitor electrode and at least one other portion that is a second battery electrode. An electrolyte is in contact with both the first conductor and the second conductor. In some embodiments, the hybrid electrochemical cell further includes a separator between the first conductor and the second conductor to prevent physical contact between the first conductor and the second conductor, while facilitating ion transport between the first conductor and the second conductor.

The disclosed technology generally relates to energy storage devices, and more particularly to energy storage devices comprising frustules. According to an aspect, a supercapacitor comprises a pair of electrodes and an electrolyte, wherein at least one of the electrodes comprises a plurality of frustules having formed thereon a surface active material. The surface active material can include nanostructures. The surface active material can include one or more of a zinc oxide, a manganese oxide and a carbon nanotube.