Generally an "inner toothed" star washer is used. Sometimes a "captive" lockwasher is built into the nut.. No washer between the cable and the solenoid itself. I lost count of how many starter cable connections I had to clean over the years. Remove the cable, sand both sides of the cable connector, apply a liberal coat of battery terminal grease and make sure there is a toothed washer (or even a split lock washer, although less effective) and torque firmly - but not TOO tight because it is only a copper bolt and often also a copper or brass nut. Steel nuts rust.