The electrochemical performances of Li4Mn5O12 powders prepared via an aqueous sol-gel method using either citric acid or l-lysine as complexing and combusting agent are compared. At current rate of 0.1 C, a discharge capacity of 163 mAh g−1 and a good cyclability are obtained for powder cathode materials prepared with l-lysine and processed as composite electrode. Films of the corresponding Li4Mn5O12 were deposited by direct spray coating of precursors' solutions and subsequent thermal treatment at 400 °C. Films exhibit better electrochemical performances than powders with a discharge capacity of up to 165 mAh g−1 at 0.1 C and a capacity retention of 95% after 100 cycles at 0.5 C and 89% after 100 cycles at 2 C. Increasing the active material loading up to 2 mg cm−2 leads to a small loss of cyclability, especially at high cycling rates, but a specific capacity of 275 μAh cm−2 is still achieved at 2 C. These values of specific capacities are higher than those observed in the literature for lithium manganese oxide films.