A Li[Li0.2Ni0.4Mn0.4]O2 cathode material for lithium battery was synthesized in de-ionized water, ethanol and ethanol with PEG by a combustion method. XPS analysis shows that Ni and Mn are in 3+ and 4+ oxidation states, respectively. Three materials exhibit a layered hexagonal α-NaFeO2 structure, and that prepared in ethanol with PEG displays the best homogeneous morphology in a size distribution of 200–400 nm. The electrochemical tests show that the material prepared in ethanol with PEG displays the best cyclic performance and rate capability, such as the discharge capacity of 254 mAhg−1 in the first cycle at 0.1C and 234 mAhg−1 after 50 cycles. Capacity retention is more than 90% after 50 cycles for the cell with a charge/discharge pre-cycling treatment (one cycle at 4.5–2.0 V and followed by one cycle at 4.8–2.0 V) compared with that without pre-cycling. EIS measurements demonstrate that pre-cycling treatment leads to form a better SEI layer and the cell assembled with the material prepared in ethanol with PEG has the least R SEI and R ct values.