Merge pull request #1097 from pybamm-team/issue-1096-sei-bug

#1096 fix sei typo

CHANGELOG.md

@@ -18,6 +18,7 @@ This release enables the use of [Google Colab](https://colab.research.google.com
 
 ## Bug fixes
 
+-   Fixed a bug in `InterstitialDiffusionLimited` ([#1097](https://github.com/pybamm-team/PyBaMM/pull/1097))
 -   Fixed `Simulation` to keep different copies of the model so that parameters can be changed between simulations ([#1090](https://github.com/pybamm-team/PyBaMM/pull/1090))
 -   Fixed `model.new_copy()` to keep custom submodels ([#1090](https://github.com/pybamm-team/PyBaMM/pull/1090))
 -   2D processed variables can now be evaluated at the domain boundaries ([#1088](https://github.com/pybamm-team/PyBaMM/pull/1088))

pybamm/models/submodels/interface/sei/interstitial_diffusion_limited.py

@@ -34,11 +34,12 @@ def get_coupled_variables(self, variables):
             "Inner " + self.domain.lower() + " electrode sei thickness"
         ]
         phi_s_n = variables[self.domain + " electrode potential"]
+        phi_e_n = variables[self.domain + " electrolyte potential"]
 
         if self.domain == "Negative":
             C_sei = self.param.C_sei_inter_n
 
-        j_sei = -pybamm.exp(-phi_s_n) / (C_sei * L_sei_inner)
+            j_sei = -pybamm.exp(-(phi_s_n - phi_e_n)) / (C_sei * L_sei_inner)
 
         alpha = 0.5
         j_inner = alpha * j_sei