This might be helpful

https://se.mathworks.com/solutions/power-electronics-control/battery-models.html

I made a battery model in PSCAD which takes into account the SOC using the coulomb count method. You can implement something similar in simulink also.

Method PSCAD Battery Model

SOC and SOH battery modeling in simulink

you can use Matlab Electrical Engineering library to do

and design your model very easily

you can find out the helping material here

https://www.mathworks.com/solutions/power-electronics-control/battery-models.html