Improving electrochemical performance of LiNi0.9Co0.05Mn0.05O2 cathode material by coating with nano-LiNbO3 layer

Abstract

The nano-LiNbO3 layer coated LiNi0.9Co0.05Mn0.05O2 (LNbO-LNCMO) cathode material was synthesized by using a facile solid-state reaction method. The starting materials, Ni0.9Co0.05Mn0.05(OH)2 precursor, lithium hydroxide (LiOH．H2O), and ∼500 nm niobium pentoxide (Nb2O5) powders, were mixed and then one-step sintered at high temperature to obtain the resultant powder. Examinations via SEM/EDS, XPS and FE-TEM revealed a ∼10 nm LiNbO3 layer on the surface of the resultant LNbO-LNCMO. The LNbO-LNCMO showed discharge capacities of 218.6 and 171.8 mAh/g at discharging rates of 0.1 and 5.0 C, respectively. These results improved the corresponding values for a pristine LNCMO sample at 212.3 and 105.1 mAh/g. After 50 charge/discharge cycles, the LNbO-LNCMO retains 93.3 % of its initial capacity, compared with an 80.6 % retention rate for pristine LNCMO. EIS and PITT analyses show that the electronic resistance of LNbO-LNCMO is much lower than that of pristine LNCMO and the higher apparent Li+ ion diffusion coefficients are obtained. The LNbO-LNCMO also show an improved thermal stability over the pristine LNCMO according to DSC analysis. These results confirm that a nano-LiNbO3 layer on the surface of LNCMO significantly reduces the reactions between electrode materials and electrolytes, which improves electrochemical performance. In this regard, the simple synthesis process with nanoparticle modification offers a promising new approach for the battery industry to fabricate novel cathode materials with high performance.