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Li 1.2 (Mn 0.32 Ni 0.32 Fe 0.16 )O 2 (LMNFO) nanoparticles with and without a chelating agent (adipic acid) were synthesized by sol–gel method. The supercapacitive behaviors of the synthesized materials as a cathode are evaluated with activated carbon (AC) as the anode in a hybrid supercapacitor (HSC) configuration utilizing a non-aqueous electrolyte. The structural, morphological and electrochemical features of the prepared materials are investigated using X-ray diffraction, scanning electron microscopy and cyclic voltammetry (CV) and charge–discharge studies, respectively. The results demonstrated that the LMNFO nanoparticles prepared with the chelating agent, adipic acid (AA), delivered an enhanced specific discharge capacitance (86 F g −1 ) and better cycling stability than the native compound. The CV studies also revealed the same conclusions, based on the stronger current response observed during various scan rates between 0 and 3 V. Moreover, the AA-LMNFO/AC cell delivered maximum energy and power densities of 36 Wh kg −1 and 1.67 W kg −1 , respectively, with a columbic efficiency of over 99% and excellent rate performance.

The kinetic properties of Li insertion in NASICON-type Li 3 V 2 (PO 4 ) 3 cathodes were enhanced substantially by Al 3+ and Cl − multivalent substitutions of various concentrations. Pristine and carbon coated, Al-doped Li 3 V 2 (PO 4 ) 3 were also prepared by a conventional solid-state approach under optimized conditions. Samples phase purity was investigated through X-ray diffractometry. Li insertion was studied in half-cells at 3-4.8 V vs. Li for the removal of 3 mol of Li. Carbon-coated Li 3 V 1.98 Al 0.02 (PO 4 ) 2.99 Cl 0.01 showed the highest reversible insertion of 2.71 mol of Li (178 mAh g −1 ) at a current density of 0.2 mA cm −2 . It showed a capacity retention of over 80% after 100 cycles. Cl − substitution led to improved performance under harsh conditions of 15 C rate and high temperature (50 °C). The enhancement of Li ion kinetics was demonstrated through cyclic voltammetry in a two-electrode configuration and electrochemical impedance spectroscopy confirmed the enhanced conductivity.

Cobalt porphyrin (CoP)-modified glassy carbon electrode (GCE) with single-walled carbon nanotubes (SWNTs) and Nafion demonstrated a higher electrocatalytic activity for the reduction of dioxygen in 0.1 M H 2 SO 4 solution. Cyclic and hydrodynamic voltammetry at the CoP-SWNTs/GCE-modified electrodes in O 2 -saturated aqueous solutions was used to study the electrocatalytic pathway. Compared with the CoP/GCE-modified electrodes, the reduction potential of dioxygen at the CoP-SWNTs/GCE-modified electrodes was shifted to the positive direction and the limiting current was greatly increased. Especially, the Co(TMPP)-SWNTs/GCE-modified electrode was catalyzed effectively by the 4e − reduction of dioxygen to water, because hydrodynamic voltammetry revealed the transference of approximately four electrons for dioxygen reduction and the minimal generation of hydrogen peroxide in the process of dioxygen reduction.