Journal of Power Sources, Vol.364, 272-279, 2017
Enhanced electrochemical performance of Li(1.2)Ni(0.13)CO(0.13)Mr(0.54)O(2) by surface modification with the fast lithium-ion conductor Li-La-Ti-O
The drawbacks of Li-rich layered oxides, such as large initial irreversible capacity, phase transformation and electrochemical performance degradation, are closely related to the surface states of the Li-rich layered oxide. To overcome these problems, a new surface modification method to the Li-rich layered oxide is proposed, in which the fast lithium-ion conductor (Li-La-Ti-O composite, LLTO) is coated on the surface of Li1.2Ni0.13Co0.13Mn0.54O2 (LRO) particles. SEM, EDS and HRTEM analyses reveal that an entire and homogeneous coating layer is formed. Electrochemical performances display that the LLTO coated samples, especially the LRO-LLTO5 material, exhibit better cycle stability, higher rate capabilities and less voltage decay. To investigate the origins of enhanced electrochemical performances for LLTO coated samples, the electrode processes at various cycles and the structural stability of the samples are studied by EIS and DSC. The protective effect of LLTO coating layer to the bulk crystallographic structure of cathode material is revealed by HRTEM images. Our study shows that the reduced interface impedances and definitely protective effect resulting from the complete and homogeneous LLTO coating layer are responsible for the enhanced electrochemical performances of the LLTO coated samples. (C) 2017 Elsevier B.V. All rights reserved.