Dear Sahil,

Porous nano tubes comprised of MnO2 nano sheets were fabricated with a one-pot hydrothermal method using polycarbonate membrane as the template. The diameter and thickness of nano tubes can be controlled by choice of the membrane pore size and the chemistry. The porous MnO2 nano tubes were used as a supercapacitor electrode. The specific capacitance in a three-electrode system was 365 F g−1 at a current density of 0.25 A g−1 with capacitance retention of 90.4% after 3000 cycles. An asymmetric supercapacitor with porous MnO2 nanotubes as the positive electrode and activated graphene as the negative electrode yielded an energy density of 22.5 Wh kg−1 and a maximum power density of 146.2 kW kg−1; these values exceeded those reported for other MnO2 nanostructures. The supercapacitor performance was correlated with the hierarchical structure of the porous MnO2 nanotubes.

Successful formation of the MWCNT-NiO nanocomposite was confirmed with techniques such as transmission electron microscopy, scan electron microscopy , electron dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy. The supercapacitance behaviour of both the symmetry and the asymmetry MWCNT-NiO based supercapacitor in 1 M H2SO4 and 1 M Na2SO4 electrolytes was evaluated using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic constant current chargedischarge (CD) techniques. There was a good correlation between the CV and the CD specific capacitance values for the asymmetry supercapacitor. Asymmetry supercapacitor (MWCNTNiO|H2SO4|MWCNT) gave the highest SC value of 925.9 mFcm-2. High SC values which are higher than most of those reported in literature were obtained. The electrodes demonstrated high stabilities with no significant changes in SC values over 1000 cycles. Nickel and cobalt (Ni-Co) binary oxide nanosheets with mesoporous structure are prepared by a facile approach based on the formation and disassociation of nickel/cobalt-citrate complex, and they show an ultra-high Faradaic capacitance up to 1846 F g−1 and excellent rate capability. On this basic, advanced aqueous asymmetric supercapacitors (AASs) are successfully built by using the Ni-Co oxide as the positive electrode and three kinds of activated carbons respectively as the negative electrode

The synthesised MO and nanocomposite films were characterised using techniques such as transmission electron microscopy, scan electron microscopy , electron dispersive X-ray spectroscopy and X-ray diffraction spectroscopy. The supercapacitance of the asymmetry MWCNT-MO based supercapacitor in 1 M H2SO4 and 1 M Na2SO4 electrolytes was measured using cyclic voltammetr, electrochemical impedance spectroscopy and galvanostatic constant current charge-discharge techniques. The asymmetry supercapacitors MWCNT-Fe2O3|MWCNT and MWCNT-Co3O4|MWCNT gave the highest specific capacitance  values of 439.94 mFcm-2 (or 64.74 Fg-1) and 425.83 mFcm-2 (or 45.79 Fg−1) respectively in 1 M H2SO4 using charge-discharge technique. Results obtained from charge-discharge experiment are much higher compared with those obtained using the CV technique since it is the most reliable and accurate method. The values compared favorably and higher compared to those reported in literature using similar technique. MWCNT-Fe2O3|MWCNT cell gave specific power (SP) and specific energy (SE) of 19.31 Wkg-1 and 2.68 WhKg-1 respectively in 1 M H2SO4, while the energy deliverable efficiency (h/%) of the cell is 99.6 and 91.3% in 1 M H2SO4 and 1 M Na2SO4 respectively.

 Regards,

Prem Baboo

https://www.researchgate.net/post/In_asymmetric_supercapacitors_metal_oxides_are_used_as_which_type_of_electrode_And_what_about_reduced_graphene_oxide?_tpcectx=profile_questions

https://www.researchgate.net/post/working_potential_range_and_cell_voltage_of_symmetric_and_asymmetric_supercapacitor?_tpcectx=profile_questions

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Same question I am also waiting for the Answer

the aim of using asymmetric electrode is to expand the voltage window so that the optimum energy density can be achieved. thus, the strategy is to select the electrodes with different voltage window so that the sum of each can be used for the voltage operation.

however, i am wondering about any rule to achieve both high energy density and power density. is it always true that if I have a high specific capacitance for each electrode then i will get a high energy density and power density? if anyone can comment on my answer, I would really appreciate that.

best,

efi

Hello dear Sahil Thareja,

Plaese have a look to the following steps (as an example) for asymmetric cell configuration Prepare two electrodes with your powder. You probably need a polymer binder and carbon black in addition to your material to fabricate the electrodes. The weight ratio of the active material: binder: carbon black is usually 85:5:10. 2) Prepare the PVA gel electrolyte (need to slightly heat the solution and constantly stir it to fully dissolve PVA powder). Generally, 1 g PVA powder per 10 mL water. 3) Dip your two electrodes in the PVA gel electrolyte. Let the electrodes be fully soaked by the gel electrolyte. Take the electrodes out and hang them for a while to let excessive gel flow down. 4) Sandwich a piece of a separator in between the two soaked electrodes. The separator can be wetted by the gel electrolyte prior to the assembly. 5) Wrap the sandwiched structure with parafilm or other films to well seal the device. This sealing step is critical as PVA can gradually dry when exposed in the air which results in capacitance loss. 6) Gently press the two electrodes to improve the filtration of the gel electrolyte and the contact between the two electrodes.

Hello Efi Dwi Indari,

The high specific capacitance never means that you have always high power/energy it also depend son many factors such as 1) the current density value 2) the potential window as we know that E = 0.5 C*V2, so it means that i depends two times higher than the capacitance of the electrode material. it means that if you have larger value at the nominator and you can divide it by smaller value than you will achieve higher value and vice versa.

First you have to dip the separator in electrolyte and then assemble the two electrodes. Also, you can add drops of electrolyte when separator dried.