Nanoscale Manipulation of Spinel Lithium Nickel Manganese Oxide Surface by Multisite Ti Occupation as High‐Performance Cathode

A novel two-step surface modification method that includes atomic layer deposition (ALD) of TiO₂ followed by post-annealing treatment on spinel LiNi_0.5 Mn_1.5 O₄ (LNMO) cathode material is developed to optimize the performance. The performance improvement can be attributed to the formation of a TiMn₂ O₄ (TMO)-like spinel phase resulting from the reaction of TiO₂ with the surface LNMO. The Ti incorporation into the tetrahedral sites helps to combat the impedance growth that stems from continuous irreversible structural transition. The TMO-like spinel phase also alleviates the electrolyte decomposition during electrochemical cycling. 25 ALD cycles of TiO₂ growth are found to be the optimized parameter toward capacity, Coulombic efficiency, stability, and rate capability enhancement. A detailed understanding of this surface modification mechanism has been demonstrated. This work provides a new insight into the atomic-scale surface structural modification using ALD and post-treatment, which is of great importance for the future design of cathode materials.