Are the cells actually in contact with each other and also what are the thermal boundary conditions to dissipate the heat - convection boundary.

Yesterday I made a new project and tried to remake the battery in the paper with the same dimensions to compare results and to verify my working method. This is what happens when boundary conditions are the same on all the cell walls: 


This is the result when I remove all boundary conditions on the cells in the middle. This clearly looks much better and compares better to the results in the paper. The cells have 3 to 7mm space in between them. The space is filled with air in the simulation (also was wondering if I need to define this area with air?). At the cells on the outside convection happens and the cells on the inside conduction I suppose? Anyway I'm not sure how I can use conduction in Ansys.

Here you can see the boundary conditions used on the cells on the outside. But what should I use for the cells on the inside because conduction isn't listed in the BC interface. I found shell conduction but this asks me for a wall thickness.