Analysis of the Phase Stability of LiMO2 Layered Oxides (M = Co, Mn, Ni)

Abstract

Transition-metal (TM) layered oxides have been attracting enormous interests in recent decades because of their excellent functional properties as positive electrode materials in lithium-ion batteries. In particular LiCoO2 (LCO), LiNiO2 (LNO) and LiMnO2 (LMO) are the structural prototypes of a large family of complex compounds with similar layered structures incorporating mixtures of transition metals. Here, we present a comparative study on the phase stability of LCO, LMO and LNO by means of first-principles calculations, considering three different lattices for all oxides, i.e., rhombohedral (hR12), monoclinic (mC8) and orthorhombic (oP8). We provide a detailed analysis—at the same level of theory—on geometry, electronic and magnetic structures for all the three systems in their competitive structural arrangements. In particular, we report the thermodynamics of formation for all ground state and metastable phases of the three compounds for the first time. The final Gibbs Energy of Formation values at 298 K from elements are: LCO(hR12) −672 ± 8 kJ mol−1; LCO(mC8) −655 ± 8 kJ mol−1; LCO(oP8) −607 ± 8 kJ mol−1; LNO(hR12) −548 ± 8 kJ mol−1; LNO(mC8) −557 ± 8 kJ mol−1; LNO(oP8) −548 ± 8 kJ mol−1; LMO(hR12) −765 ± 10 kJ mol−1; LMO(mC8) −779 ± 10 kJ mol−1; LMO(oP8) −780 ± 10 kJ mol−1. These values are of fundamental importance for the implementation of reliable multi-phase thermodynamic modelling of complex multi-TM layered oxide systems and for the understanding of thermodynamically driven structural phase degradations in real applications such as lithium-ion batteries.

Investigating the Structural and Electronic Properties of LiMO2 (M: Mn, Ni, Co) as Potential Cathode Materials: A DFT Study

“…The stead-fast demand for sustainable lithium-ion batteries (LIB) with competitive electrochemical properties, safety, reduced costs, and long-life cycle, calls for intensive efforts towards the development of new battery cathode materials 1 . In previous investigations focusing on the LIB positive electrode materials, the transition metal oxides (NMC) layered type cathodes have been attracting considerable attention due to their capability to optimize the capacity, cyclic rate, electrochemical stability and lifetime 2,3 . The transition metals Mn, Ni and Co have been reported to contribute in different ways towards enhancement of the performance of NMC based lithium-ion batteries 2 .…”

Replacement of Cobalt in Lithium-Rich Layered Oxides by n-Doping: A DFT Study

“…An effective value of U-J = 4.00 eV has been used for all Co, Ni, and Mn d electrons. This value is an average between the values of Co, Mn, and Ni, reported from ab-initio UHF calculations, and has been recently validated by us for LiMO 2 layered phases (M = Co, Ni, Mn) [44][45][46]. We used a kinetic energy cut-off of 520 eV and Brillouin Zone sampled at the Gamma point.…”

“…where x is the stoichiometric coefficient (0.12, 0.08, 0.04, and 0), and E tot values are the electronic total energies calculated at the DFT+U level of each species. The thermodynamic properties of Li 2 MnO 3 , LiMnO 2 , LiCoO 2 , and LiNiO 2 have been evaluated by us in a previous work at the same level of theory [46]. We can approximate formation energy at 0K with the standard formation enthalpy at 0 K, i.e., ∆ form E 0K ∆ form H • 0K .…”

Effect of LiCoO2-Coated Cathode on Performance of Molten Carbonate Fuel Cell

“…Therefore, the cell performance is expected to improve by the expanded TPBs of the LiCoO 2 -coated cathode. Furthermore, the pore structure of the coating can be maintained stably because LiCoO 2 has higher rigidity than lithiated NiO, which is used as the cathode material [14][15][16]. If the pore structure of the cathode collapses, gas diffusion and electrolyte impregnation through the pores are inhibited.…”