AlN is an alternative candidate for the in situ coating because of its high electrical resistivity and high compatibility with Li. In this case, Al and N are doped into Li to enhance AlN formation at the sur­face of vanadium alloy substrates. The coating has shown sufficient resistivity and stability under ther­mal cycling.

In this process, however, Li needs to be saturated with N to prevent the dissolution of the AlN layer. With a high N level in Li, vanadium alloy not covered with the AlN layer will get N from Li and become brittle. This issue was observed in high-temperature
capsule tests with Mo and vanadium alloys.15’16 Thus, unless the vanadium alloy channel walls are fully covered with AlN, the use of this coating tech­nique seems problematic. For the same reason, the use of AlN layers, sheets, or plates in Li as the insulator requires full coverage of the vanadium alloy structures with AlN.