Secondary batteries are used as the energy supplier of mobile electronic devices which are not renounceble in daily life. Especially secondary lithium batteries are preferred because of their high energy density. For such batteries, the first parameter effecting the energy density is the surface area and thus particle size of the materials which make up cathode and anode. In this study; LiCoO 2 is used as active cathode material in secondary lithium batteries synthesized by sol-gel method. The change of particle size of cathode material synthesized by using LiNO 3 and Co(NO 3) 2 with calcination temperature was investigated. X-ray analysis showed that LiCoO 2 reached its best crystal form and its biggest particle size at 750°C.