A new synthetic route of LiNi0.5Mn0.5O2 was proposed (named ‘hydroxide mud method’), much more simplified synthetic method without filtering, washing and repeated heat treatment processes. By dropping LiOH to the aqueous solution of metal (Ni, Mn) nitrates, hydroxides of metals were precipitated and the resulting solution was evaporated as received (without filtering or washing of the precipitate). The dried mixture was added with ethyl alcohol (to dissolve and disperse Li salts) and processed with specially devised three-step heat treatment. Synthesized material showed no impurity phase (examined by X-ray diffraction, XRD) and high discharge capacity about 175mAh/g (3–4.6V cut-off voltage range).