The ratio of anode active material to cathode active material is an important factor in the design of different energy storage devices (LIBs, LICs,…).
In theoretical works, this mass ratio is calculated using the masses of active material of one anode and one cathode. For a coin cell this ratio is correct because we have two electrodes. However, in a pouch cell normally the number of electrodes is not equal. In this case, sometimes the outer electrodes are one sided (the active material is only in one face). Therefore, the mass ratio is similar to that of two electrodes. But in some cases, the outer electrodes are double sided (the active material is placed in the two faces) and the current collector has holes. Therefore, the outermost active material takes part in the electrochemical reactions. In this last case, how do we calculate the mass ratio? I think we have to take into account the total mass of the active materials that are in the cell. Is it correct?
Thank you
Dear Jose,
The situation that you describe is not trivial. Of course, the outer surface of the electrodes will participate in the charge-discharge process, but the charging conditions for it will be strongly different because of the different diffusion pathways and charge distribution. As a result, its SOC will be always lower than that of the inner parts of the cell. If you just want to calculate the theoretical capacity of the cell this can be described by multiplication of the mass of the active material at the outer surface by some coefficient between 0 and 1. But if you need more detailed modelling of the battery behaviour, the special charging conditions of the surface material will probably become the most important part of the model that affects the degradation of the cell during cycling.
Dear Alexander,
Thank you for your answer. Really, the simulation of such a system is not a trivial issue. The election of the coefficient you mentioned (0-1) has to be adequate to fit the behaviour of the cell. However, from the viewpoint of cell design, this outer mass could affect the theoretical cell performance. For example, the ratio of anode active material to cathode active material is related the specific energy density of LICs, as pointed in this recent work:
https://www.researchgate.net/publication/260758217_Theoretical_guidelines_to_designing_high_performance_energy_storage_device_based_on_hybridization_of_lithium-ion_battery_and_supercapacitor
I have no very clear if this outer active material improves the specific energy density of the cell, or not.
Article Theoretical guidelines to designing high performance energy ...
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Energy