Do you think the good (energy density) battery cell (EV-44) from Electrovaya changed Toyota's mind?  No, it couldn't have been that!  Maybe it was because of the safety record of the EV-44 cell that they are familiar with?  Or, the fact that the solid state cell is so much better than anything out there that they would gain tremendous market share?  In any case Toyota knows what Electrovaya has and has had experience dealing with them.