TiO2 surface modified LiNi0.5Mn1.5O4 cathode powder synthesis using different temperatures for lithium ion batteries

Abstract

Average LNMO diameter ± std. error (nm) SEM TEM Smaller LNMO particles N/A 34 ± 2 Larger LNMO particles 575 ± 73 N/A • Using an anneal at 500°C; Ti atoms were found to dope at the LNMO surface. Increasing the annealing temperature to 800 o C caused these Ti atoms to diffuse towards the core. Above 750°C, a slight amounts of secondary LiNi 0.5 Mn 1.5-x Ti x O 4 spinel phase were formed. • A surface modification followed by an anneal at 500°C improves cycle life, CE% and rate performance. This is probably due to incorporation of stronger Ti-O bonds within the spinel LNMO surface structure, which reduces the Mn dissolution into the electrolyte upon cycling. Introduction Conclusions References Results LiNi 0.5 Mn 1.5 O 4 is surface modified with TiO 2 (LNMO@TiO 2). The effects of annealing under oxygen atmosphere between temperatures of 500 to 850°C on Ti 4+ positions, morphology, crystal structure and electrochemical performance are investigated. A sol-gel approach is used to homogeneously modify the surface of ~30-500 nm diameter LNMO core particles with TiO 2. Metal oxide shell synthesis on LNMO through wet-chemical routes usually results in amorphous deposits [1-3]. The shell is then crystallized by high temperature anneals; ranging from 500 to 800°C [1-4]. The annealing temperature and atmosphere deserve, however, special attention, since these can cause Ti diffusion from the shell towards the surface or bulk of the LNMO particles, as well as causing changes in cation ordering inside the LNMO. Ti surface doping is useful in increasing the LNMO's structural stability, while excess Ti doping may cause capacity drops [5]. In this study, we aimed to increase the cycle life of LNMO, by modifying the LNMO surface with titanium oxide, while at the same time, avoiding bulk doping. Region Ni (at%) Mn (at%) Ti (at%) Mn/Ni S1 28.9 63.1 7.9 2.2 C1 29.0 70.0 1.0 2.4 S2 26.2 68.5 5.2 2.6 C2 27.0 69.3 3.7 2.6 Cycle 10