It will be better if you share your eq, or how you have defined your generation term.
Generally, if you are using the comsol default eq in which this term is present, then., use Eq view subnode, look for the generation term syntax and use it in the derived values after getting the solution.
or, if you have manually defined the generation term in variable node, then use that term in the derived values, like I mentioned earlier.
I hope it helps. Lemme know if you have further query.
Create a 3D model of the Li-ion battery in COMSOL Multiphysics software. This can be done using the CAD import or geometry creation tools in the software.
Define the materials used in the battery, including the electrodes, separator, and electrolyte. You can obtain the material properties from literature or experimental data.
Set up the physics involved in the battery, including the electrochemical reactions, heat transfer, and mass transport. In the electrochemical reaction module, you can define the charge and discharge reactions of the battery. In the heat transfer module, you can define heat generation due to Joule heating and the exothermic reactions.
Apply the appropriate boundary conditions, including the current density, temperature, and concentration at the electrodes and the ambient conditions outside the battery.
Run the simulation and analyze the results. The heat generation value can be obtained from the heat flux density at the electrodes or the total heat generated in the battery.