We found that muSR detects Li-diffusion in LixCoO2, LiNiO2, Lix(NiCoMn)O2 and LiFePO4 through a dynamic behavior of nuclear field relaxation. Very recently, we have also found that Na- and K-diffusion are successfully detected by muSR in NaxCoO2 (0.5<x<0.75) and K0.67CoO2, despite the mass difference between Li, Na, K and muon. This is because, since muon is identified as an ideal point charge, muon is located at the vicinity of oxygen anions so as to make a stable mu-O bond. However, in order to complete the muSR work on Na- and K-diffusion and compare the muSR result with that of the past electrochemical measurements, we wish to request a continuation experiment on NaxCoO2 (x<0.5) and KxCoO2 (0.5<=x<0.67). Particularly, since there are neither K-NMR nor electrochemical studies on K-diffusion in KxCoO2, the proposed experiment will provide a unique insight on ion-diffusion in solids.