Effect of annealing temperature on crystal structure and lithium ion battery performance of TiO2 surface modified LiNi0.5Mn1.5O4

Abstract

High energy and power density lithium ion batteries (LIB) are extensively being studied for their potential applications in portable electronics and hybrid/full electric vehicles as well as for their ability to store solar, wind and other renewable energies with high efficiency [1]. LiNi 0.5 Mn 1.5 O 4 (LNMO) attracts attention as a high voltage cathode material (4.7 V vs. Li/Li +) with good capacity (147 mAh/g); having potential for high power applications [2]. However, cyclic stability of LNMO still remains an issue since all cathode materials containing Mn are challenged with capacity fade problem due to Mn leaching within commercial electrolytes [1]. Introducing a shell layer on LNMO that is stable at high voltages can prevent Mn dissolution and increase cycle life; while also enabling good conductivity, if ionically and electronically conductive [3]. Materials such as Li 4 Ti 5 O 12 [4] , Li 2 TiO 3 [5] and TiO 2 [4] attract attention as shell material candidates in literature, owing to their structural stability within organic electrolytes at high voltages, as well as their 3D Li + diffusion paths allowing good ionic conductivity. TiO 2 is used as the surface modification material in this work; synthesized using a sol-gel approach. Different from previous studies; effect of different annealing temperatures (500 to 850 o C) on Ti 4+ diffusion from surface towards the core of LNMO is investigated. Electrochemical performances are compared while also considering the ordering/disordering changes within the LNMO crystal structure.