[Maxx92]

 Hello,

I'm trying to calculate the reversible reaction heat during charging and discharging of a Lithium-Ion Battery. Additionally Im trying to calculate the irreversible reaction heat of a battery that occurs as a result of high current.

The positive active material of the Battery is LiNiMnCoO2 (NMC).
The reaction equalation ist (M = Metal: Ni,Mn,Co):



For the reversible heat during charging and discharging applies Q = dS * T. To calculate dS I need the Standard reaction enthalpy and the Gibbs free energy for Li Ni Mn Co O2. I would do it like in this picture:



Here is an other example for calculating the heat during charging and discharging of a Nickel-Metalhybrid (NiMH) battery:





Result:

dS * T for 25 °C Q1 = dS * T = 29,3 kJ/H2 mol

They also calculated the irreversible heat, as a result of reaction of the electrolyt with the electrons occurs as a result of high current:



Results:
Standard reaction enthalpy dH = -285,9 kJ/mol
And for the reversible heat T * dS = -48,6 kJ/mol (bei 25 °C)

They also use this equalation, I'm not sure why:



To calculate the reaction heat that occurs as result of high current, they used dH:

Qreact = dH

Gibbs free energy: dG = dH - dS * T.

dS * T describes the Transformation of during charging and discharging emerging Energie in heat and dH the Transformation of the energy in mechanical work. I think this is the reason why they used dH.

Chemistry is not my strongest skill, so i would be glad, if someone could help me.

Kind regards Maxx