Electrolyte effect on electrochemical behaviors of manganese fluoride material for aqueous asymmetric and symmetric supercapacitors

Exploring wide voltage window materials is not only an available measure to enhance the energy density of hybrid supercapacitor(HSCs),but also avoids the dynamic mismatch caused by different energy storage mechanisms of two electrodes in assembled symmetrical HSC.However,there are few reports about the wide potential window materials except Bi_(2)O_(3)and VO_(2).Therefore,the MnF_(2)synthesized by solvothermal reaction was served as the electrode for HSC.The MnF_(2)exhibited electrochemical activity in alkaline solution in three-electrode system,especially with a wide potential window from-0.8 to+0.5 V in 2 mol·L^(-1)NaOH.Furthermore,the assembled MnF_(2)//MnF_(2)symmetrical HSC had a potential window of 1.5 V,and it exhibited outstanding long-cycle capability.Meanwhile,when MnF_(2)was taken as the negative and positive respectively,the potential windows of asymmetric devices CoMoO_(4)//MnF_(2)and MnF_(2)//Activated Carbon(AC)could reach 1.3 and 1.45 V,respectively,showing excellent cycle stability.This work shows that MnF_(2)material has great research value in HSC,and provides a new research direction for developing high-performance devices.

Recrystallization texture development in rare-earth(RE)-doped non-oriented silicon steel

High-grade non-oriented silicon steel with higher permeability and lower core loss has become the pursed target with the rapid developnient of electrical machines.The effects of rare-earth(RE)element on recrystallization texture in RE-doped Fe-3.1 wt.%Si-1.2 wt.%Al non-oriented silicon steel were investigated by macro-and micro-texture analyses.Nonlinear variation of recrystallization texture with RE element content was observed.In the competition among main recrystallization texture components,favorable{113}<361>and X fiber(<001>//ND)are strengthened and unfavorable y fiber is evidently decreased by the addition of RE element,whereas the effect of RE element is reversed by excess RE element.The recrystallization texture development is determined by RE-affected nucleation and grain growth in terms of grain boundary migration related to segregation and inclusion.The properly inhibited grain boundary mobility can promote favorable recrystallization texture by the improved nucleation and efficient grain growth.

Perovskite fluoride NaNiF_(3) with hollow micron sphere structure as anode for Li-ion hybrid capacitors

Lithium-ion hybrid capacitors(LIHCs) are gaining more attention and applications because they break the performance limitations of supercapacitors(SCs) and lithium-ion batteries(LIBs).However,the difference of energy storage mechanism between anode and cathode is a problem that must be faced by Li-ion hybrid capacitors.The selection of suitable anode and cathode materials is one of the effective ways to solve this problem.Here,we synthesized hollow spherical perovskite fluoride NaNiF3 by a simple and safe method.The specific capacity of NaNiF3 is 142 mAh·g^(-1) at 0.1 A·g^(-1) for 1000 cycles.The mechanism in the cycling of NaNiF3 electrodes was investigated using ex situ X-ray photoelectron spectroscopy(XPS),which is typical of the conversion reaction.Meanwhile,the NaNiF_(3)//activated carbon(AC) Li-ion hybrid capacitor assembled and showed better energy density(69 Wh·kg^(-1)) and power density(5699 W·kg^(-1)).Its capacity retention after long cycling was 79%.The use of NaNiF3 expands the choice of electrode materials for LIHCs and extends their practical applications.