In Situ Formation of a Cathode–Electrolyte Interface with Enhanced Stability by Titanium Substitution for High Voltage Spinel Lithium-Ion Batteries

Although LiNi0.5Mn1.5O4 (LNMO) high-voltage spinel is a promising candidate for a next generation cathode material, LNMO/graphite full cells experience severe capacity fading caused by degradation reactions at electrode/electrolyte interfaces and consequent active Li+ loss in the cells. In this study, it is first reported that in situ formation of a Ti–O enriched cathode/electrolyte interfacial (CEI) layer on a Ti-substituted LiNi0.5Mn1.2Ti0.3O4 (LNMTO) spinel cathode effectively mitigates electrolyte oxidation and transition metal dissolution, which improves the Coulombic efficiency and cycle life of LNMTO/graphite full cells. The Ti–O enriched CEI layer is produced in situ during an initial cycling of LNMTO as a result of selective Mn and Ni dissolution at its surface, as evidenced by various surface characterizations using X-ray photoelectron spectroscopy, transmission electron microscopy, time-of-flight secondary ion mass spectrometry, Raman spectroscopy, and synchrotron-based soft X-ray absorption spectroscopy. The Ti–O enriched CEI has an advantage over traditional LNMO powder coatings, namely the formation of conformal CEI without compromising electronic conduction pathways between cathode particles.