Primary Li carbonate is produced direct from the primary circuit in the Lithium plant - concentrated brine is reacted with sodium carbonate to precipitate Lithium carbonate.
Battery grade has additional processing in the purification circuit - lithium carbonate is reacted with CO2 to produce soluble lithium bicarbonate which is then cleaned up by ion exchange before precipitating lithium carbonate again.
It seems that much of what they are selling from the primary circuit is being purchased for further processing to lithium hydroxide, hence their plans to build a LiOH plant and for stage 2 to dispense with the purification circuit.
This may help in regards to understanding the differences in the grades they sell.
http://www.toyotsumaterial.co.jp/en/jigyo/pdf/Li Carbonate_Battery.pdf
http://www.toyotsumaterial.co.jp/en/jigyo/pdf/Li Carbonate_Technical.pdf
http://www.toyotsumaterial.co.jp/en/jigyo/pdf/Li carbonate Prime(2018).pdf
http://www.toyotsumaterial.co.jp/en/jigyo/pdf/Li carbonate Industrial(2018).pdf
