Enhui Liu

Perovskite KNi0.8Co0.2F3 nanocrystals for supercapacitors

Perovskite KNi0.8Co0.2F3 nanocrystals were introduced as potential electrode materials for supercapacitors, which exhibited superior specific capacity and rate behavior owing to the optimal synergistic effect of Ni and Co redox species. The AC//KNi0.8Co0.2F3 asymmetric capacitor delivered high power and energy densities together with excellent cycling stability.

Ternary Ni-Co-F Nanocrystal-Based Supercapacitors

Ternary nickel cobalt fluoride (Ni-Co-F) nanocrystals are constructed solvothermally for use as the positive electrode materials in supercapacitors. The optimal Ni-Co-F (Ni/Co=2:1) shows slight chemical shifts in X-ray diffraction (XRD) data and X-ray photoelectron spectra (XPS) compared with bare Ni-F and Co-F. The Ni-Co-F (Ni/Co=2:1) exhibits typical square nanocrystal morphology together with a mesoporous surface structure, as observed through TEM observations and nitrogen sorption measurements. Owing to the stronger synergistic effect of Ni and Co redox species originated from the richer Ni and Co surface electroactive sites, Ni-Co-F (Ni/Co=2:1) shows superior performances of specific capacitance, rate capability, and charge-transfer kinetics (564 F g-1 at 1 Ag-1 , 418 F g-1 at 16 Ag-1 , 449 Ω) compared with all the other Ni-Co-F candidates. Moreover, the activated carbon (AC)//Ni-Co-F (Ni/Co=2:1) asymmetric capacitor designed based on charge balance delivers superior energy and power densities (18.4 Wh kg-1 , 6.64 kW kg-1 ) together with longer cycle life (77 % retention after 10 000 cycles at 4 A g-1 ).

Fe3+/Fe2+ redox electrolyte for high-performance polyaniline/SnO2 supercapacitors

Abstract The Fe 3+ /Fe 2+ redox electrolyte for use in polyaniline/tin oxide (PANI/SnO 2 ) supercapacitors was reported. The influences of redox electrolyte based on different Fe 3+ /Fe 2+ ion pair concentrations in 1 mol/L H 2 SO 4 solution on the pseudocapacitive behaviors of PANI/SnO 2 supercapacitor were investigated. The electrochemical properties of the supercapacitor were studied by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. It is found that the performance of the supercapacitor is the best when the Fe 3+ /Fe 2+ concentration is 0.4 mol/L and its initial specific capacitance is 1172 F/g at an applied current density of 1 A/g. The long-term cycling experiment shows good stability with the retention of initial capacitance values of 88% after 2000 galvanostatic cycles. The experimental results testify that using Fe 3+ /Fe 2+ redox electrolyte has a good prospect for improving the performances of energy-storage devices.

Bimetallic Co-Mn Perovskite Fluorides as Highly-Stable Electrode Materials for Supercapacitors

Bimetallic Co-Mn perovskite fluorides (KCox Mn1-x F3 , denoted as K-Co-Mn-F) with various Co/Mn ratios (1:0, 12:1, 6:1, 3:1, 1:1, 1:3, 0:1) were prepared through a one-pot solvothermal strategy and further used as electrode materials for supercapacitors. The optimal K-Co-Mn-F candidate (Co/Mn=6:1) showed a size range of 0.1-1 μm and uniform elemental distribution; exhibiting small changes in XRD peaks and XPS binding energy in comparison to the bare K-Co-F and K-Mn-F, due to the structural/electronic effects. Owing to the stronger synergistic effect of Co/Mn redox species, the K-Co-Mn-F (Co/Mn=6:1) electrode exhibited superior specific capacity and rate behavior (113-100 C g-1 at 1-16 Ag-1 ) together with excellent cycling stability (118 % for 5000 cycles at 8 Ag-1 ), and the activated carbon (AC)//K-Co-Mn-F (Co/Mn=6:1) asymmetric capacitor showed superior energy and power densities (8.0-2.4 Wh kg-1 at 0.14-8.7 kW kg-1 ) along with high cycling stability (90 % for 10 000 cycles at 5 Ag-1 ).