Designing Hierarchical Assembly of Lanthanum-Doped TiNb₂O₇ for Single-Crystalline Cathodes: An Approach to Improving Cyclability at High Rates and Voltages

Abstract

Nickel-rich NMC cathodes are currently the most promising electrode materials for lithium-ion batteries (LIBs) because of their development and application perspectives. However, structural instabilities during electrochemical cycling, lattice oxygen loss, and interfacial side reactions have been significant issues exacerbated at high voltages, compromising their cyclic stability and safety. Herein, we demonstrate a cost-effective wet chemical solution route to deposit thin TiNb 2 O 7 (TN) and Ti 0.95 La 0.05 Nb 2 O 7 (TNL) shells on the LiNi 0.83 Mn 0.06 Co 0.11 O 2 (NMC-83) cathode and study the effect of surface modification on the electrochemical properties. X-ray diffraction and electron microscopy verify that the NMC-83 particles are unaffected by the thin-layer TN and TNL coatings. Electrochemical tests indicated that the TNL coating improved the lithium-ion kinetics at a high voltage of 4.5 V. The 0.2 mol % TNL-coated NMC-83 discharged 141.88 mA h/g after 140 cycles at 0.5C and maintained 77.4% of the initial discharge capacity. By contrast, the 0.2 mol % TN-coated NMC-83 and pristine NMC-83 cathodes discharged only 132.36 and 119.76 mA h/g, respectively, with capacity retention of 72.7 and 63.2%. Even at 2C, the TNL coating material retained a capacity of 43.59% at the end of 150 cycles. The TNL coating paves the way for next-generation LIBs by providing stable, high-performance, and high-capacity cathode materials.