Boosting ultrafast Li storage kinetics of conductive Nb-doped TiO₂ functional layer coated on LiMn₂O₄

Interface engineering of LiMn₂O₄ (LMO) is a promising strategy to enhance the lithium storage capability and cycling stability of cathode materials in Li-ion batteries (LIBs). This is because the strategy prevents structural degradation; however, Li storage kinetics remains unsatisfactory, resulting in poor ultrafast cycling performance. Therefore, we fabricated an Nb-doped TiO₂ (NTO) functional layer as a conductive passivation layer on the LMO surface by horizontal ultrasonic spray pyrolysis deposition. The NTO functional layer suppressed the volume expansion of LMO and exhibited high electrical and ionic conductivity, which resulted in improved structural stability of LMO (related to cycling stability) and increased electron/ion transfer rate (related to ultrafast cycling performance). In the TiO₂ structure, Ti⁴⁺ ions were replaced by Nb⁵⁺ ions, which possess high electrical conductivity and a wide c-axis as a Li-ion diffusion route. As a result, the NTO-coated LMO cathode material showed an outstanding specific capacity of 112.7 mAh/g with a remarkable capacity retention of 96.2% after 100 cycles at a current density of 1 C and excellent ultrafast cycling capacity and stability of 70.0 mAh/g after 500 cycles at a current density of 10 C.