Role of Ni, Mn and Co in Layered Rock Salt Cathode Materials for Li-Ion Battery: A DFT Study

Li-ion battery (LIB) has high energy/power density and long cycle life among other battery systems. LiCoO2(LOC) is a commonly used LIB cathode material which has a layered rock salt structure. To meet environmental needs, especially for the reduction of CO2, electrification of the automotive applications requires high volume of batteries. Here, Co which is a key element of LIB has potential supply risks due to its geological availability and value chains. Although, low-Co and high Ni cathode materials such as LiNiMnCoO2 (NMC) or LiNiCoAlO2 (NCA) have been developed by Edisonian approach, the role of Co in the cathode materials with layered rock salt structure is still not clear. To understand the role of Co, we conducted a comprehensive study with modeling and simulation backed up by the synchrotron X-ray experiment. A series of density functional theory (DFT) calculation was performed using the Vienna Ab initiation Simulation Package (VASP)[1,2] within the projector augmented-wave method and generalized-gradient approximation (GGA). All calculations were performed employing PBE-GGA+U. Change in the charge density distributions and thestructure parameters at different states of charge (SOCs) were calculated for mono-transition-metal oxidessuch as LCO, LiNiO2 (LNO) and LiMnO2 (LMO) as well as ternary-transition material NMC with different composition ratio, ie NMC111, NMC622, NMC811. Figure 1 shows Bader charge analysis[3] result for each elements in LCO, LNO and LMO as a function of the SOC. Detailed analysis with experimental results of XAFS and XRD, and will be discussed in the meeting. [1] P. E. Blöch, Phys. Rev. B 50, 17953 (1994). [2] G. Kresse et al., Phys. Rev. B 59, 1758 (1999). [3] G. Henkelman, A. Arnaldsson, and H. Jónsson, Comput. Mater. Sci. 36, 354-360 (2006) Figure 1