I am newbie to battery materials. As I understand, specific capacity of a battery-type material can be expressed in term of C/g or mAh/g and can be calculated from the cyclic voltammetry (CV) or galvanostatic charge-discharge (GCD) curves.
The papers that I have found show only how to calculate specific capacity in mAh/g.
Specific capacity (mAh/g) from CV: C=∫Idv/(2*3.6*m*v)
Specific capacity (mAh/g) from GCD: C=I∆t/(3.6*m)
where ‘∫Idv’ implies area under the CV curve, ‘m’ signifies mass (g) of active electrode, ‘v’ specifies the scan rate, ‘I’ implies current intensity, '∆t' is discharge time.
Please guide me how to calculate specific capacity in C/g?
If possible, please show me a reference with the detailed calculation or formula.
Thank you so much.
I found the answer after asking my friend who experienced in battery!!!
mAh/g = 3.6 A.s/g = 3.6 C/g
Therefore, to calculate specific capacity (C/g) from CV and GCD:
Specific capacity (C/g) from CV for battery: C=∫Idv/(2*m*v)
Specific capacity (C/g) from GCD for battery: C=I∆t/(m)
In the case of calculating specific capacitance (F/g) from CV and GCD:
Specific capacitance (F/g) from CV for supercapacitors: C=∫Idv/(2*m*v*(Vf-Vi)
Specific capacitance (F/g) from GCD for supercapacitors: C=I∆t/m(Vf-Vi)
(Vf-Vi) is the potential window.
I found the answer after asking my friend who experienced in battery!!!
mAh/g = 3.6 A.s/g = 3.6 C/g
Therefore, to calculate specific capacity (C/g) from CV and GCD:
Specific capacity (C/g) from CV for battery: C=∫Idv/(2*m*v)
Specific capacity (C/g) from GCD for battery: C=I∆t/(m)
In the case of calculating specific capacitance (F/g) from CV and GCD:
Specific capacitance (F/g) from CV for supercapacitors: C=∫Idv/(2*m*v*(Vf-Vi)
Specific capacitance (F/g) from GCD for supercapacitors: C=I∆t/m(Vf-Vi)
(Vf-Vi) is the potential window.
Dear Do Van Lam ;
The electrochemical capacitive performance can be calculated by the representative galvanostatic charge-discharge curves. The average specific capacitance values, Cs (F g-1), of the samples were estimated from the discharge process according to eqn.:
Cs(F g-1)= I.∆t /∆V.m
where I is the charge-discharge current loaded (A), ∆t is the discharge time (s), ∆V is the potential change during the discharge process, and m is the mass of the active material within the electrolyte (g).
for more details can read the attached reference;
Dear Mahmood H. M.,
Actually, I was looking for the specific capacity (C/g), not specific capacitance (F/g).
I found the answer after asking a friend who is working in the battery research.
Thank you so much for your response and the nice reference.
Coulomb= Amp* sec
Farad= Amp*sec/volt.
the integrated area under CV curve is the Amp* volt.
So the specific capacity (C/g) from CV: C= Amp* volt/(2* mass* (volt/sec))
= Amp * sec/ 2* mass = C/g
Dear Do Van Lam ,
it is recommended to calculate the specific capacity (C/g) of a battery, from the GCD-mode [batteries: I.∆t/(m)],
since it offers an upper hand (over CV-mode) to know, more precisely[1], (and individually) uniquely, the specific capacities (both) at the 1)discharge, or/and the
2)charge
semi-cycle phase(s), vice versa.
1. Plainly, measure, only, the time ∆t, during either the 1)discharge (-I), or/and 2)charge (+I), semi-cycles' phases.
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