I would start with this blocK: https://www.mathworks.com/help/physmod/sps/ref/batterytablebased.html
this block will let you chose pre-parameterized models from certain vendors.
Capacity and internal impedance aren't enough data to capture the many complexities of a lithium ion battery. They are certainly good enough for a basic simulation especially if you are more focused on the rest of the circuit performance, but if you need to study aging, detailed SOC estimation, etc. a much more thorough battery characterization process is needed. So either you need a lot of data from the vendor, or you have to set up your own battery characterization test.
