Lithium manganese oxide (LiMn2O4) had been a promising material for lithium-ion and thin film batteries. However, the LiMn2O4 had some problems such as the manganese dissolution into liquid electrolyte. In order to improve cycleability, we introduced SnOx layer as protective layer. This layer was deposited on spinel LiMn2O4 by using radio frequency magnetron sputtering. The deposited SnOx layer fully covered the LiMn2O4 , and didn’t make a change the crystallinity of the spinel films. The SnOx layer prevented direct contact of liquid electrolyte and improved the cycle retention.