Conceptually, the current way to do that would be to put in a battery with 100% capacity, set the meter so it shows 100% when it is actually 80% and put however this works in the system to halt charging at (actual) 80% while showing 100%. We see 100% but behind the scenes, it's this same 80% charged (actual) store of power.
And maybe tweak that gauge with some inspiration from Spinal Tap so that a dial that normally maxes at 10 could go up to 11 and thus "be louder, because it goes to 11" by making the PRO MAX option make the above option make the (actual) 80% display as 110%, so PRO MAX users can enjoy "10% more battery."
To what you probably want though is an actual 100% capacity able to be effectively charged to 100% over and over with no consequence. For that, a new kind of battery technology will need to be discovered and invented beyond the one used now.