New solution to instability of spinel LiNi0.5Mn1.5O4 as cathode for lithium ion battery at elevated temperature

In this work, we proposed a new solution to the instability of LiNi0.5Mn1.5O4 cathode for lithium ion battery by simply controlling discharge end-off voltage. The morphology and the crystal structure of LiNi0.5Mn1.5O4 before and after cycling at elevated temperature were characterized with XRD and SEM, and its performances as cathode of lithium ion battery were investigated by cyclic voltammetiy and galvanostatic chargedischarge tests. It is found that the cyclic stability of LiNi0.5Mn1.5O4 at elevated temperature is significantly improved by changing the end-off discharge voltage from 3.5 V to 4.0 V (vs. Li+/Li). After 500 cycles with 1 C rate at 55 C the capacity retention rate of LiNi0.5Mn1.5O4 is only 16.8% for the end-off discharge voltage of 3.5 V, but improves to 84.9% for 4.0 V. The improved stability is attributed to the limitation of the reduction of Mn4+ to Mn3+ that causes the primary particle separation of LiNi0.5Mn1.5O4. (C) 2013 Elsevier B.V. All rights reserved.