Manganese phosphate (Mn(PO) hexagonal micro-rods and (Mn(PO) with different graphene foam (GF) mass loading up to 150mg were prepared by facile hydrothermal method. The characterization of the as-prepared samples proved the successful synthesis of Mn(PO) hexagonal micro-rods and Mn(PO)/GF composites. It was observed that the specific capacitance of Mn(PO)/GF composites with different GF mass loading increases with mass loading up to 100mg, and then decreases with increasing mass loading up to 150mg. The specific capacitance of Mn(PO)/100mg GF electrode was calculated to be 270Fg as compared to 41Fg of the pristine sample at a current density of 0.5Ag in a three-electrode cell configuration using 6M KOH. Furthermore, the electrochemical performance of the Mn(PO)/100mg GF electrode was evaluated in a two-electrode asymmetric cell device where Mn(PO)/100mg GF electrode was used as a positive electrode and activated carbon (AC) from coconut shell as a negative electrode. AC//Mn(PO)/100mg GF asymmetric cell device was tested within the potential window of 0.0-1.4V, and showed excellent cycling stability with 96% capacitance retention over 10,000 galvanostatic charge-discharge cycles at a current density of 2Ag.

This work presents the effect of different contents of graphene foam (GF) on the electrochemical capacitance of nickel phosphate Ni3(PO4)2 nano-rods as an electrode material for hybrid electrochemical energy storage device applications.

Highlights •NiCo/NiCoMn-mixed hydroxides, ternary NiCo-MnO 2 nanostructures were successfully synthesised. •The samples were used as electrodes for electrochemical supercapacitor in 1 M KOH. •The electrode materials exhibit good charge storage capability on both regions. •Assembled NiCo-MnO 2 /C-FP hybrid supercapattery displays high electrochemical performance.

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VS 2 nanosheets as the positive electrode and the activated carbon (AC) as the negative electrode with a 6 M KOH solution as electrolyte were fabricated as an asymmetric supercapacitor. These materials were combined to maximize the specific capacitance and to enlarge the potential window, therefore improving the energy density of the device. A specific capacitance of 155 F g -1 at 1 A g -1 with a maximum energy density as high as 42 Wh kg -1 and a power density of 700 W kg -1 was obtained for the asymmetric supercapacitor within the voltage range of 0 -1.4 V. The supercapacitor also exhibited a good stability with ∼ 99% capacitance retention and no capacitance loss after 5000 cycles at a current density of 2 Ag -1 .

Low cost porous carbon materials were produced from cheap polymer materials and graphene foam materials which were tested as a negative electrode material in an asymmetric cell configuration with α-MoO3 as a positive electrode.

An asymmetric supercapacitor fabricated with CoAl-layered double hydroxide/graphene foam (LDH/GF) composite as the positive electrode and activated carbon derived from expanded graphite (AEG) as negative electrode in aqueous 6 M KOH electrolyte is reported. This CoAl-LDH/GF//AEG cell achieved a specific capacitance of 101.4 F g -1 at a current density of 0.5 A g -1 with a maximum energy density as high as 28 Wh kg -1 and a power density of 1420 W kg -1 . Furthermore, the supercapacitor also exhibited an excellent cycling stability with ∼ 100% capacitance retention after 5000 charging-discharging cycles at a current density of 2 Ag -1 . The results obtained show the potential use of the CoAl-LDH/GF//AEG material as suitable electrode for enhanced energy storage as supercapacitor.

Highlights• Synthesis of activated carbon (AC) from the carbonisation of polypyrole (PPY).• KOH activation of the AC to produce porous carbons.• Symmetric device based on the porous AC exhibit good electrochemical performance.• Supercapacitor show excellent stability based on potentiostatic floating test for 200 h AbstractThis work present the synthesis and electrochemical performance of mesoporous carbon material derived from the activation and carbonisation of polypyrole (PPY). Electrochemical performance of the PPY derived carbon was investigated in a two electrode cell in a 6 M KOH alkaline electrolyte. The symmetric device was subjected to floating test (voltage holding) for ~200 h at a voltage of 1.2 V and the specific capacitance as well as the resistance of device was determined after every 10 h of floating. The device exhibited a specific capacitance of 179 F g -1 at 0.5 A g -1 and 158 F g -1 at 10 A g -1. In addition, after floating for ~120 h the resistance was constant with a very slow decrease in capacitance.2 Beyond ~120 h, a quick decrease in capacitance was observed with a corresponding increase in resistance, indicating a possible deterioration to the electrodes. Remarkably, at the end of floating, the specific capacitance calculated at 5 A g -1 was 120 F g -1 (~25% decay in capacitance from the initial value 160.5 F g -1 at 5 A g -1) suggesting good stability of the device over a long period of time (~8 days).