Aqueous Supercapacitors With Wide Operative Voltage Window and Long Cycling Life Enabled by Electrolyte Hybridization Effect

Developing supercapacitors(SCs)with long cycling life and wide operative voltage window is a significant topic in the field of aqueous electrolytes.Although the design of water in salt(WIS)electrolytes has pushed the development of aqueous electrolytes to a new height,the WIS electrolytes with an operative voltage window of up to 2.5 V is still very scarce.Herein,in order to enrich the type of aqueous electrolyte with high operative voltage,tetramethylammonium trifluoromethanesulfonate(TMAOTf)based WIS electrolyte was used as a model to construct WIS based hybrid electrolyte with acetonitrile(ACN)co-solvent and LiTFSI co-solute.In view of the coordination effect of ACN and Lit on free water in TMAOTf based WIS electrolyte,the TMAt-Lit-AWIS electrolyte has the electrochemical stabilization window of up to 3.35 V.Further coupled with the commercial YP-50F electrodes,TMAt-Lit-AWIS based SCs exhibited wide operative voltage window(2.5 V),long cycling life(45,000 cycles)and good low-temperature performance(99.99%capacitance retention after 2000 cycles at20℃).The design of this hybrid electrolyte will enrich the types of aqueous hybrid electrolytes with long cycling life and wide operative voltage window.

Effects of Ta on the solidification behavior and microstructure of a rhenium-containing hot corrosion resistant single crystal

The effects of Ta on the solidification microstructure of the Re-containing hot corrosion resistant Ni-base single crystal were investigated. Results showed that Ta addition significantly modified the solidification behavior and further influenced the as-cast microstructure. Ta addition changed the solidification characteristic temperatures and decreased the segregation of refractory elements (Re and W) as well as increased the solidification temperature range from 39.0 to 61.8℃ as Ta addition increased from 2wt% to 8wt%. The integration of these two factors increased the primary dendrite arm spacing and changed the morphology and size of γ′ precipitates. With increasing Ta addition from 2wt% to 8wt%, the size of γ′ precipitates in the dendrite core increased substantially from 0.24 to 0.40 μm, whereas the γ′ precipitates in the interdendritic region decreased slightly from 0.56 to 0.47 μm. This paper then discussed the mechanism of these “Ta effects”.