Fine-Tuning Cathode Performance: The Influence of Argon Deposition Pressure on LiMn2O4 Thin Film Electrochemistry for Li-Ion Batteries

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.