LiOH and Li₂CO₃ are impurities remaining in NCM (Ni, Co, Mn Oxide) cathode powder in its manufacturing. As the sources of battery swelling, they need to be removed to a very low level from the cathode material. The existing technique for removing these impurities is wet washing with such as water. N₂ and NF₃ mixed gas from a multi layered DBD (Dielectric Barrier Discharge) plasma can remove the LiOH and Li₂CO₃ in dry environment. We monitored the reaction product gas coming from the conversion reaction by QMS residual gas analyzer. The O₂ and CO₂ concentration was increased in the conversion reaction of LiOH and Li₂CO₃ respectively. The addition of little amount of H₂ gas into the mixed gas increased the dissociation rate of the NF₃ molecule. In that condition, the O₂ concentration was decreased in LiOH conversion whereas the CO₂ concentration was steeply increased in Li₂CO₃ conversion. This plasma process could remove up to 80% of impurities of LiOH and Li₂CO₃ from 622 NCM powder in just one minute.