NAi/Li Antisite Defects in the Li1.2Ni0.2Mn0.6O2 Li-Rich Layered Oxide: A DFT Study

Abstract

Li-rich layered oxide (LRLO) materials are promising positive-electrode materials for Li-ion batteries. Antisite defects, especially nickel and lithium ions, occur spontaneously in many LRLOs, but their impact on the functional properties in batteries is controversial. Here, we illustrate the analysis of the formation of Li/Ni antisite defects in the layered lattice of the Co-free LRLO Li1.2Mn0.6Ni0.2O2 compound through a combination of density functional theory calculations performed on fully disordered supercells and a thermodynamic model. Our goal was to evaluate the concentration of antisite defects in the trigonal lattice as a function of temperature and shed light on the native disorder in LRLO and how synthesis protocols can promote the antisite defect formation.

Li-Rich Layered Oxides: Structure and Doping Strategies to Enable Co-poor/Co-free Cathodes for Li-Ion Batteries

“…Currently these diffraction lines are considered a clue of the existence of an unresolved superstructure with Li2MnO3 symmetry crystallizing in a monoclinic layered structure that adopts a C2/m space group (mC24), as reported in figure 1b. [14][15][16] In this lattice, Li ions occupy inter-slab octahedral sites (4h and 2c) and slab octahedral sites (2b and 4g) together with Mn ions in (1:2) ratio, whereas oxygen atoms occupies 4i and 8j sites. The layered structure of Li2MnO3 is often described by using the notation Li[Li1/3Mn2/3]O2 where Mn ions are partially replaced by Li ions and Li + and Mn 4+ form a locally ordered honeycomb structure.…”

“…In fact, several groups demonstrated the presence of multiple thin planar defects along the transition metal layers and report these defects as stacking faults [21,[29][30][31] or as defect-point, anti-site defect. [16,32,33] Moreover, structural properties vary with the composition and with the synthetic technique used, from precursor mixing and annealing conditions. [34][35][36][37] The structural ambiguity of LRLOs directly reflex on to the sluggish rationalization of the corresponding redox mechanism in batteries and the unsatisfactory comprehension of the structural evolution occurring during repeated cycles of electrochemical lithiumions extraction/insertion.…”

“…A rationalization of the impact of the annealing temperature on transport properties was proposed by Tuccillo et al using DFT and partially-disordered supercells: apparently the formation of large concentration of Ni/Li antisite defects between TM and Li layers can easily occur at temperatures larger than 700°C. [16] Also in the case of Co-free LRLOs, isovalent and aliovalent metal doping (including Na + , Nd 3+ , Al 3+ , Fe 3+ , F -, S 2-, SO4 2-and PO4 3-) [104][105][106][107][108][109][110] was used as effective strategy to improve structural stability and decrease voltage decay upon long-term cycling. For instance, Manthiram et al [109,110] reported a systematic study on the influence of cationic substitution on the reversible capacity of the first Manthiram suggested the possible inhibition of oxygen redox reaction by a tailored doping of the LRLO lattice.…”

Unraveling The Role of Oxygen and Manganese Charge Compensation During Nucleation and Crystal Growth of Li-rich Layered Li1.2Mn0.8O2 Cathode Materials

“…11 Current developments emanating from the application of computational materials science to secondary battery research work hand-in-hand with experimental material developments with a focus on the redox-active battery components. 12 Of particular interest, is the contribution of classical molecular dynamics (MD) as it has proven to capably incorporate microstructural features not easily included at the DFT scale. This makes it a much-better-suited candidate for calculating long-range diffusion, allowing simulations over longer time and length scales.…”

“…Overall, these methods pave the way for a rational design of materials and can help the understanding of complex phenomena in batteries, such as voltage hysteresis, voltage decay, or anionic redox reactions in superlattices and transport dynamics in electrode materials. 12 Current trends concerning the application of computational materials science to secondary battery research follow the parallel experimental material developments, thus focusing on the redox-active components, either negative or positive electrodes, as well as electrolytes and interfaces. 12,13 The prediction of the structures of materials at the atomic level is one of the main goals of current computational materials science.…”