Improving the rate capability of LiNi0.5Mn1.3Ti0.2O4 by modifying the lithium insertion mechanism

Abstract

Since lithium-ion batteries are becoming increasingly popular, we aimed to increase the power density of lithium-ion batteries by improving the rate capability of lithium insertion electrodes by controlling the reaction mechanism of lithium insertion materials. LiNi0.5Mn1.3Ti0.2O4 (Ti-LNMO), in which a part of Mn4+ in LiNi0.5Mn1.5O4 (LNMO) was replaced by Ti4+, was synthesized and proceeded in a single-phase reaction over the entire region. This resulted in two types of LNMOs with the same spinel structures and solid-state redox reactions of Ni2+/Ni4+, each with different reaction mechanisms. According to rate-capability tests of these two types of LNMOs, the Ti-LNMO exhibited superior rate capability than the LNMO without Ti-substitution, which demonstrated that high-power capabilities could be achieved by controlling the reaction mechanism. Furthermore, the solid-state Li-ion diffusion coefficient in the LNMOs was determined from the rate-capability using the diluted electrode method, and that of Ti-LNMO was more than three times greater than that of the LNMO. These results reveal that the lithium insertion mechanism is important for the kinetics of lithium insertion reaction.