Effects of protecting layer [Li,La]TiO3 on electrochemical properties of LiMn2O4 for lithium batteries

A sample of LiMn₂O₄ spinel oxide was surface-modified with lithium lanthanum titanate (Li,La]TiO₃), which was developed as a lithium ionic conductor, by means of hydrothermal processing and subsequent heat treatment at 400 °C. The surface coating layers were analyzed by morphology observation using a transmission electron microscopy. Energy-dispersive spectrometry and X-ray photoelectron spectroscopy were used for element investigation. The surface modification effects on rate capability during cycling and capacity retention for the LiMn₂O₄ spinel oxide were confirmed. Then Mn dissolution during storage at elevated temperatures of the pristine, coated sample was characterized. The Mn dissolution characterization was based on the idea that Mn dissolution is one of the most significant reasons for capacity loss for LiMn₂O₄ spinel oxide, and this phenomenon is especially severe at elevated temperatures. Our experimental results indicate that the surface-modified sample shows much a better initial capacity and rate capability compared with the pristine sample. The Li,La]TiO₃ coating effectively enhances the structural stability of LiMn₂O₄ at elevated temperatures, most likely because the Li,La]TiO₃-modifying layers play a definitive role in suppressing Mn dissolution in the electrolyte during storage.