Lithium manganese oxide (LiMn₂O₄) is an effective cathode material for high-capacity lithium-ion (Li-ion) batteries. Therefore, to optimize battery efficiency, it is essential to understand how sputtering deposition conditions affect the quality and performance of LiMn₂O₄. This research examines how argon deposition pressure affects the stoichiometric characteristics and electrochemical performance of LiMn₂O₄. The study finds that changing argon deposition pressures, from a low of 5 mTorr to a high of 30 mTorr, results in the formation of different coating stoichiometries. At low argon deposition pressures, stoichiometric LiMn₂O₄ cathode coatings formed, exhibiting the highest discharge capacity of 115 mAh/g. Conversely, at high argon deposition pressures, non-stoichiometric LiMn₂O₄ with lithium deficiency was produced. These coatings exhibited diminished electrochemical behavior, achieving a discharge capacity of only 70 mAh/g at 5 mTorr. The lack of lithium resulted in a significant reduction in electrochemical performance, indicated by a high surface charge transfer resistance (R₂ = 48,529 Ω), which led to a low discharge capacity of 40 mAh/g.