Advanced asymmetrical supercapacitors based on graphene hybrid materials

Abstract

Supercapacitors operating in aqueous solutions are low cost energy storage devices with high cycling stability and fast charging and discharging capabilities, but generally suffer from low energy densities. Here, we grow Ni(OH) 2 nanoplates and RuO 2 nanoparticles on high quality graphene sheets in order to maximize the specific capacitances of these materials. We then pair up a Ni(OH) 2 /graphene electrode with a RuO 2 /graphene electrode to afford a high performance asymmetrical supercapacitor with high energy and power density operating in aqueous solutions at a voltage of ~1.5 V. The asymmetrical supercapacitor exhibits significantly higher energy densities than symmetrical RuO 2 -RuO 2 supercapacitors or asymmetrical supercapacitors based on either RuO 2 -carbon or Ni(OH) 2 -carbon electrode pairs. A high energy density of ~48 W·h/kg at a power density of ~0.23 kW/kg, and a high power density of ~21 kW/kg at an energy density of ~14 W·h/kg have been achieved with our Ni(OH) 2 /graphene and RuO 2 /graphene asymmetrical supercapacitor. Thus, pairing up metal-oxide/graphene and metal-hydroxide/graphene hybrid materials for asymmetrical supercapacitors represents a new approach to high performance energy storage.

NiCo2S4 Nanosheets Grown on Nitrogen‐Doped Carbon Foams as an Advanced Electrode for Supercapacitors

“…The mass ratio of NiCo 2 S 4 to OMC/NCF was controlled at about 0.21 in the ASCs based on the principle of charge balance at 5 mV s −1 for both electrode (see experiment methods). Referring to previous reports, the carbon material exhibits a typical characteristic of a electric double-layer capacity in an electrolyte of KOH aqueous solution within the range −1.0−0 V. [41][42][43] NiCo 2 S 4 based material display excellent electrochemical reversibility within a potential window of −0.1−0.6 V. [ 23,27 ] Therefore, it is expected that the work voltage of ASCs device can be extended to 1.6 V. We performed a series of CV and charge/ discharge measurements with increasing voltage windows to estimate the best operating potential of the designed ASCs device ( Figure S8a,c, Supporting Information). More capacitive response from Faradaic reactions will occur with the increasing operating potential.…”

Graphene-Wrapped Sulfur Particles as a Rechargeable Lithium–Sulfur Battery Cathode Material with High Capacity and Cycling Stability

“…[18][19][20][21][22][23][24][25][26] Recently we have developed a two-step method to grow metal hydroxides and oxides nanocrystals with interesting morphologies and nanoscale sizes on graphene sheets with various degrees of oxidation and surface functional group coverage. [18][19][20][21][22] As a result of controlled nucleation and growth, the hydroxide or oxide nanomaterials are selectively formed on graphene with intimate interaction to the conducting graphene substrate. The strong electrical coupling renders the otherwise insulating active materials conducting, which significantly increases the specific capacitance (capacity) and rate capability of the graphene hybrid or composite electrode materials.…”

Synthesis, Properties and Potential Applications of Porous Graphene: A Review

“…Thus, supercapacitors could be employed in various applications such as portable electronics and electrical vehicles [50]. Generally, based on the design of the electrodes and on the different energy storage mechanism involved, there are two types of supercapacitors: the electrical doublelayer capacitors (ECDL) based on ion adsorption and the pseudo-capacitors in which the energy is stored through redox reactions [91,92]. The materials studied so far for supercapacitors are carbon [93], activated carbon [94,95], metal oxides [96], carbon nanotubes [97,98].…”