# Changing Stoichiometry of Individual Electrodes

**URL:** <https://pybamm.discourse.group/t/changing-stoichiometry-of-individual-electrodes/192>\
**Category:** Parameters\
**Created:** [20 February 2025 07:53 UTC](https://pybamm.discourse.group/t/changing-stoichiometry-of-individual-electrodes/192 "2025-02-20T07:53:07Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![vipulnovo](https://avatars.discourse-cdn.com/v4/letter/v/f19dbf/32.png) [@vipulnovo](https://pybamm.discourse.group/u/vipulnovo)\
**Post date:** [20 February 2025 07:53 UTC](https://pybamm.discourse.group/t/changing-stoichiometry-of-individual-electrodes/192/1 "2025-02-20T07:53:07Z")

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Hi everyone,

I was wondering if it’s possible to change the stoichiometry of individual electrodes in PyBaMM. Specifically, I’m looking to adjust the stoichiometry for the anode and cathode independently. Is there a way to do this within the current framework?

EDIT:  
Even though the input OCP is a function of stoichiometry, I am observing a difference in the individual capacities of the electrodes as per the design. This discrepancy is affecting the overall capacity calculations. Could someone advise on how to approach or resolve this issue? Any insights or suggestions would be greatly appreciated.

Any guidance or pointers to relevant examples would be greatly appreciated!

Thanks in advance!

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**Author:** ![valentinsulzer](https://yyz2.discourse-cdn.com/free1/user_avatar/pybamm.discourse.group/valentinsulzer/32/9_2.png) [@valentinsulzer](https://pybamm.discourse.group/u/valentinsulzer)\
**Post date:** [26 February 2025 18:22 UTC](https://pybamm.discourse.group/t/changing-stoichiometry-of-individual-electrodes/192/2 "2025-02-26T18:22:20Z")

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The easiest way is probably to change the maximum concentration to affect the electrode capacities, and change the initial concentrations to affect the lithium balance

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**Author:** ![Salah](https://avatars.discourse-cdn.com/v4/letter/s/977dab/32.png) [@Salah](https://pybamm.discourse.group/u/Salah)\
**Post date:** [31 March 2025 13:47 UTC](https://pybamm.discourse.group/t/changing-stoichiometry-of-individual-electrodes/192/3 "2025-03-31T13:47:56Z")

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Hello if might I ask, i have 2 questions, first i’m trying to simulate an NMC622/graphite cell, so I used the OKane2022 parameters with some changes as i’m working with 119 Ah cell, the problem that I’m facing right now is that OKane2022 uses graphite-SiOx which gives the cell more capacity, i tried to change the graphite diffusity by using `graphite_diffusivity_Ecker2015` and `graphite_ocp_Ecker2015, graphite_electrolyte_exchange_current_density_Ecker2015,` but it didn’t change much so what i’m tring to do is too u see the graphite paramters from Ecker2015 and the NMC from OKane2022. is my logic makes sense or is there a better way to acheive what i’m looking for. **Second question : how can i make the OCP go abouve 4.2V like 4.3 or more?**

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**Author:** ![vipulnovo](https://avatars.discourse-cdn.com/v4/letter/v/f19dbf/32.png) [@vipulnovo](https://pybamm.discourse.group/u/vipulnovo)\
**Post date:** [15 April 2025 13:18 UTC](https://pybamm.discourse.group/t/changing-stoichiometry-of-individual-electrodes/192/4 "2025-04-15T13:18:08Z")

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the maximum concentration is calculated from Q = F × c\_max × ε\_s × L  
Where:

- **Q** is the electrode capacity in [A·h/m²]
- **F** is Faraday’s constant (96485 C/mol)
- **c\_max** is the maximum concentration of lithium in the solid phase [mol/m³]
- **ε\_s** is the volume fraction of active material in the electrode
- **L** is the electrode thickness [m]​

Exchange current density and diffusivity would change the nature of your charge or discharge curve but the parameters in your control are thickness and maximum concentration