I’m working with battery-supercapacitor hybrid device, I know that to obtain better performance charge storage in positive electrode must equal to that stored in negative electrode (Q+ = Q−), my question is how to calculate the charge storage in battery-type electrode (has peak in CV and nonlinear CD) and that for capacitor electrode, is it ok to calculate them from CV using (Idv/(msdv),or should I use CD curve (IT/3.6m) (Knowing that the battery-type electrode has potential rage (-1to +0.6) and capacitance electrode (-1 to 0.0 V) in 3 electrode system . Also I have another question: How to calculate the specific capacity and energy for this hybrid device.
Hello Zuhair Elseddig,
Here I'm giving the method to calculate specific capacitance/capacity from cyclic voltammetry (CV) and charge-discharge(CD) for 3-electrode system:
Specific capacitance (F/g) for supercapacitors calculated from CV
C=∫Idv/(m*v*(Vf-Vi)
where, ‘∫Idv’ implies area under the CV curve, ‘m’ signifies mass (g) of active electrode, ‘v’ specifies the scan rate, ‘(Vf-Vi)’ is an functional potential frame.
Specific capacity (mAh/g) for rechargeable batteries calculated from CV
C=∫Idv/(3.6*m*v)
Specific capacitance (F/g) for linear/triangular CD curve (EDLC based supercapacitor)
C=I∆t/m(Vf-Vi)
where, , ‘I’ implies current intensity, '∆t' is discharge time.
But Specific capacitance (F/g) for non-linear CD curve (pseudocapacitance based supercapacitor)
C=2I∫Vdt/m(Vf-Vi)2
'∫Vdt’ symbolizes the area under the discharge curve only.
Specific capacity (mAh/g) for rechargeable batteries calculated from CD
C=I∆t/(3.6*m)
For further information, you can see my publications as well. I'm attaching a few here.
For 2-electrode system, the 'm' will be considered as the total mass of the both electrodes involved in device fabrication. Other aspects are same.
Article Hexagonal VS2 Anchored MWCNTs: First Approach to Design Flex...
Article Free-standing flexible MWCNTs bucky paper: Extremely stable ...
Article Highly conductive energy efficient electroless anchored silv...
Dear Bidhan
Many thanks for your answers. However my question is how to calculate the charge (q) balance in both electrode (battery-electrode and capacitance electrode), because in my situation I want to design hybrid supercapacitor-battery device, so my question is should I calculate q from CD for both 2 electrodes so that I must use the following equation
m+/m- = c-*∆E-/c+*∆E+
However, when I used this equation the cell voltage (is about 1.45 V) is smaller than the single electrode (potential for battery electrode was scanned from -1 to 0.6 V ( ~ about 1.6 V) in 3 electrode system). Am I right ?
Or should I use another equation to calculate the q value for each electrode?
cf�����
Hi Zuhair Elseddig,
I have done some work on hybrid capacitors (Li-ion capacitors and Na-ion capacitors). In my opinion, it's very difficult to find the best mass ratio of cathode and anode materials or working voltage window for a hybrid capacitor (in this case, the hybrid capacitors can show the highest energy density or the best cycling performance) if you only consider the the equal q contributed from cathode and anode based on their capacities or working voltage window in half-cells or half-devices. Generally, the c and E of cathode and anode materials in half-cell or half-device are different. Even though you choose the "matching mass ratio" of cathode and anode materials, the actual c and E in full-cell or full-device might be different from those in half-cell or half-device. For example, the current in the full-device is the same for cathode and anode, but the current densities are different due to the different mass ratio of anode and cathode materials. So, many workers chose some mass ratios of cathode and anode materials when they assembled the hybrid capacitors. Then, they tested these capacitors (using GCD or CV) and determined the best one. This method looks "low tech" but it is efficient to find the capacitor with best performance. Some related works are listed below:
J. Mater. Chem. A, 2016, 4, 5149–5158;
Nano Energy 23 (2016) 129–137;
Adv. Energy Mater. 2017, 7, 1701336.
Hopefully you find them useful.
The posted items can help you to have a better understanding of the working principle, modelling, sizing and energy management based on optimized FLC of a hybrid energy system:
Article Real time energy management strategy for a fast charging ele...
Article Multi-objective Optimal Sizing and Energy Management of Hybr...
- Badges
- Science topic
- Similar topics
- Engineering
- Electrical Engineering
- Electrodes