If I understand correctly the hydrogen pressure chart, the x-axis is the mole fraction of LiH within an Li-LiH system. So LiH/(Li + LiH) and not H/Li?
source: http://tempid.altervista.org/j100612a013a.pdf
Also, do I read this right that with a 1:1 LiH:Li ratio, the pressure wouldn't exceed 25^2 Torr = 0.83 bar until a temperature of 900C?
Whereas with no lithium added, we would be on the right side of the chart and pressure would be litteraly off the chart.
So it seems that the added lithium would have a moderating effect on pressure at least until 900C.
Makes sense?