There are a lot of variables, but let's look at it this way. Let's consider a charging box with an incorporated battery fed uniquely by solar panels. You plug your i4 that is down to 10%, and you charge it. It starts at 200kW, but the curve goes down as the battery charges up, and overall, tests have shown that you'll get to 80% after about 30 minutes, after taking in from 10% to 80%, or 70% of your 80.7kWh, so 61kWh. Let's say that that box is on a fairly well used station where there is no line up for open chargers, but where over the 12 hours of sunlight, on average it is charging 50% of the time. So since it took you 30 minutes to take in your 61kWh, on average the box will be idle for another 30 minutes before somebody else connects; thus, the box must be able to dish out 61kWh per hour, or 61kW.I calculate that with 12 hours daylight 7000m2 of solar would charge around 15 i4 s from 0-100%. Is that right?! That’s a bit scary in terms of area of pvs required to power ev motor cars.
If your solar panels have the same efficiency as mine, since my 64m2 provide 12.3kW, 61kW would require 5 times 64m2, so 320 m2. Of course, the 61kW will be too weak to provide the instant power your car will initially draw, but that's why there needs to be a battery to stock the power to give you the big current when you need it and to recharge to prepare for the next car after you leave and nobody uses it for a while.
So let's imagine now a station with, say 20 charging spots, fully covered, where each spot is about 2.5 m wide by 6m long (your i4 is 1.85m wide by 4.8m long so it will fit just, plus and overhang of 3m for the roadway coming into the charging spots. Covering the charging area with solar panels requires 450m2, or only 1/14 of the capacity necessary to feed all the charging boxes (6400m2).
On the other hand, considering the biggest Gas Station/Convenience store in Texas (and possibly the world), the Buc'ees in New Braunfels, Texas; it has a 6700m2 store with fast food, toilets, and basically snacks retail, and 60 gas pumps. So a smaller scale version of that for our 20 charging spots above could have, say, a 2200m2 store, and the 450m2 covered area for the 20 charging spots, total 2650m2 of roof/solar panels, so the solar panels would provide about 40% of the energy required to feed the charging spots.
I agree that it's not really conceivable to have 100% of the charging energy provided by the solar panels, especially since there will be rainy days where the solar panels operate at much reduced power; but it can be argued that with today's technology (the solar panels efficiency are increasing every day), you can have re-charging stations where solar panels provide a substantial fraction of the total energy required.