Mines vary with 1-4% or so Li2O (1% would probably make most mines nearly non-feasible)
"A typical spodumene concentrate suitable for lithium carbonate production contains 6-7% Li2O (75% - 87% spodumene". So it's more about the purity of Spodumene at that point.
Mica content as low as possible probably, they might use other fillers more suitable for such a battery.
Further down-stream processing produces:
Industrial Grade: < 99.0% Lithium Carbonate
Technical Grade 99.0% LC
Battery Grade 99.5% LC
EV Grade 99.9% LC
EV Plus Grade 99.99% LC