Study on electrochemical performance of activated carbon in aqueous Li2SO4, Na2SO4 and K2SO4 electrolytes

Air-assisted activation strategy for porous carbon spheres to give enhanced electrochemical performance

Porous carbon spheres showing excellent pore structures and superior electrochemical performance were obtained from a resorcinol–formaldehyde resin by an air-assisted activation strategy.

Alternating voltage induced porous Co3O4 sheets: an exploration of its supercapacity properties

An alternating voltage induced method has been developed for the fabrication of porous Co₃O₄ sheets.

Investigation of different aqueous electrolytes on the electrochemical performance of activated carbon-based supercapacitors

Porous activated carbons was synthesized by an environmentally friendly technique, with an in-depth experimental study carried out to understand the electrochemical behaviour in different aqueous electrolytes (KOH, LiCl, and Na₂SO₄).

Engineering the electrochemical capacitive properties of graphene sheets in ionic-liquid electrolytes by correct selection of anions

Graphene sheet (GS)-ionic liquid (IL) supercapacitors are receiving intense interest because their specific energy density far exceeds that of GS-aqueous electrolytes supercapacitors. The electrochemical properties of ILs mainly depend on their diverse ions, especially anions. Therefore, identifying suitable IL electrolytes for GSs is currently one of the most important tasks. The electrochemical behavior of GSs in a series of ILs composed of 1-ethyl-3-methylimidazolium cation (EMIM(+)) with different anions is systematically studied. Combined with the formula derivation and building models, it is shown that the viscosity, ion size, and molecular weight of ILs affect the electrical conductivity of ILs, and thus, determine the electrochemical performances of GSs. Because the EMIM-dicyanamide IL has the lowest viscosity, ion size, and molecular weight, GSs in it exhibit the highest specific capacitance, smallest resistance, and best rate capability. In addition, because the tetrafluoroborate anion (BF4(-)) has the best electrochemical stability, the GS-[EMIM][BF4] supercapacitor has the widest potential window, and thus, displays the largest energy density. These results may provide valuable information for selecting appropriate ILs and designing high-performance GS-IL supercapacitors to meet different needs.

Energetic aqueous rechargeable sodium-ion battery based on Na2 CuFe(CN)6 -NaTi2 (PO4 )3 intercalation chemistry

Aqueous rechargeable sodium-ion batteries have the potential to meet growing demand for grid-scale electric energy storage because of the widespread availability and low cost of sodium resources. In this study, we synthesized a Na-rich copper hexacyanoferrate(II) Na2 CuFe(CN)6 as a high potential cathode and used NaTi2 (PO4 )3 as a Na-deficient anode to assemble an aqueous sodium ion battery. This battery works very well with a high average discharge voltage of 1.4 V, a specific energy of 48 Wh kg(-1) , and an excellent high-rate cycle stability with approximately 90 % capacity retention over 1000 cycles, achieving a new record in the electrochemical performance of aqueous Na-ion batteries. Moreover, all the anode, cathode, and electrolyte materials are low cost and naturally abundant and are affordable for widespread applications.

LiMn2O4 nanotube as cathode material of second-level charge capability for aqueous rechargeable batteries

LiMn2O4 nanotube with a preferred orientation of (400) planes is prepared by using multiwall carbon nanotubes as a sacrificial template. Because of the nanostructure and preferred orientation, it shows a superfast second-level charge capability as a cathode for aqueous rechargeable lithium battery. At the charging rate of 600C (6 s), 53.9% capacity could be obtained. Its reversible capacity can be 110 mAh/g, and it also presents excellent cycling behavior due to the porous tube structure to buffer the strain and stress from Jahn-Teller effects.

Core-shell sulfur@polypyrrole composites as high-capacity materials for aqueous rechargeable batteries

In order to explore the potential application of sulfur in aqueous rechargeable batteries, core-shell sulfur-polypyrrole (S@PPy) composites were prepared through a novel one-pot and surfactant-free method. Sulfur exhibits a very high capacity of 473 mA h g(-1) and good cycling stability in an aqueous Li(2)SO(4) electrolyte due to the polypyrrole coating.

Bis(2,2'-biphenoxy)borates for electrochemical double-layer capacitor electrolytes

Fluorine makes the difference! Bis(2,2'-biphenoxy)borates decorated with fluorine substituents have been synthesized and studied in supercapacitor test cells (see scheme). A clear trend towards higher electrochemical stability with the increase of the fluorine content has been observed. For a maximum performance, only two fluorine substituents per benzene moiety are required.

Electroless deposition of conformal nanoscale iron oxide on carbon nanoarchitectures for electrochemical charge storage

We describe a simple self-limiting electroless deposition process whereby conformal, nanoscale iron oxide (FeO(x)) coatings are generated at the interior and exterior surfaces of macroscopically thick ( approximately 90 microm) carbon nanofoam paper substrates via redox reaction with aqueous K(2)FeO(4). The resulting FeO(x)-carbon nanofoams are characterized as device-ready electrode structures for aqueous electrochemical capacitors and they demonstrate a 3-to-7 fold increase in charge-storage capacity relative to the native carbon nanofoam when cycled in a mild aqueous electrolyte (2.5 M Li(2)SO(4)), yielding mass-, volume-, and footprint-normalized capacitances of 84 F g(-1), 121 F cm(-3), and 0.85 F cm(-2), respectively, even at modest FeO(x) loadings (27 wt %). The additional charge-storage capacity arises from faradaic pseudocapacitance of the FeO(x) coating, delivering specific capacitance >300 F g(-1) normalized to the content of FeO(x) as FeOOH, as verified by electrochemical measurements and in situ X-ray absorption spectroscopy. The additional capacitance is electrochemically addressable within tens of seconds, a time scale of relevance for high-rate electrochemical charge storage. We also demonstrate that the addition of borate to buffer the Li(2)SO(4) electrolyte effectively suppresses the electrochemical dissolution of the FeO(x) coating, resulting in <20% capacitance fade over 1000 consecutive cycles.