You guys beat me to it
A relatively unknown brand making bold claims to gain attention is not something exactly new in the electric space
400 Wh/kg solid state battery is exciting. Along other, probably embellished claims (100 000 cycles...), the most important is probably that Donuts lab say that production costs would be lower than traditional Li-ion batteries. That is indeed the real crux of the matter, not the bit about reaching crazy high specs but manufacturing such cells on a large scale at competitive costs.
thepack.news
Anyway, to get some pointers about what it would mean, whenever that happens, let's take the current 7.2 kWh pack, at 265 Wh/kg it's 27.2 kg (in cells).
400 Wh/kg would take a battery of 27.2 kg to a capacity of 10.9 kWh (+3.7 kWh).
Alternatively, such cells would decrease the weight of a 7.2 kWh pack to 18 kg (-9.2 kg).
It's either another cheap PR stunt or someone is gonna get filthy rich, quick!
Now let's dream about that 11 kWh Varg