Tesla Model Y battery: 81 KWh, 1,700 lbs => 21 lb/KWh. (Lithium-iron phosphate)
Tesla Model 3 battery: 82 KWh, 1,060 lbs => 13 lb/KWh. (Lithium-ion)
1000KWh in lithium-ion: 13,000 lbs.
Teslarati guesses around 15,000 lbs.[1]
A typical semi-truck without trailer weighs 15,000-25,000 pounds. So 15,000 pounds of battery is not hopeless. The Hummer EV weighs 9,000 pounds, after all.
Tesla can, and probably will, sell the "extended range" version for a premium price. There are many semi-trucks that never take long trips. This is mostly a battery cost problem.
Semi's battery is not going to need as much armor.