Fundamental Linkage Between Structure, Electrochemical Properties, and Chemical Compositions of LiNi_1–x–yMn_xCo_yO₂ Cathode Materials

Abstract

LiNi1–x–y Mn x Co y O2 (NMC) is an important class of high-energy-density cathode materials. The possibility of changing both x and y in the chemical formula provides numerous materials with diverse electrochemical and structural properties. It is highly desirable to have guidance on correlating NMC structural and electrochemical properties with their chemical composition for material designing and screening. Here, using synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, electrochemical characterization, and literature survey, the content difference between Mn and Co (denoted as x–y in NMC) is identified as an effective indicator to estimate Li/transition metal (Li/TM) cation mixing ratio and first-cycle Coulombic efficiency (CE). In addition, a linear relationship between oxygen position “z” and the size difference between Li+ and TM cation (normalized by the c-axis length) is found, and such linearity can be used to accurately predict the oxygen position in NMC materials by considering the average TM cation size and c-axis length. It is also concluded that the shortest O–O distance in the bulk of NMC materials could not be shorter than 2.5 Å even at a highly charged state. Therefore, oxygen release is not likely to take place from the bulk if the structure maintains the R3 ̅m symmetry.

Enhancement of Structural, Electrochemical, and Thermal Properties of High-Energy Density Ni-Rich LiNi0.85Co0.1Mn0.05O2 Cathode Materials for Li-Ion Batteries by Niobium Doping

“…This change in this phase transition process that has a major contribution to the particle crack formation process is consistent with what was suggested in previous reports as the advantage of doping to Ni-rich NCMs. , A possible reason for the stabilization during this phase transition is the stronger Nb–O bonds. According to a recent study by Hu et al on the fundamental links between the spatial structure, electrochemical properties, and chemical composition of metal oxide cathodes, oxygen release is also a cause of surface phase changes and local stresses, which contribute to the formation of intergranular cracks . As Hu et al demonstrated in their study, our study shows a link between stronger oxygen binding (in our case via Nb–O bonds) and a reduced formation of intergranular cracks …”

Suppressing High‐Current‐Induced Phase Separation in Ni‐Rich Layered Oxides by Electrochemically Manipulating Dynamic Lithium Distribution

“…[27][28][29] Although the Li/Ni mixing ratio calculated by XRD refinement has uncertainty, the estimated Ni Li ratio seems comparable to previously reported values from NCM-based materials. [29][30][31] Detailed structural parameters and reliability factors obtained from Rietveld refinement are summarized in Table S1 (Supporting Information). A typical secondary particle morphology was observed in the scanning electron microscopy (SEM) images (Figure 1b).…”

Studies of Nickel-Rich LiNi0.85Co0.10Mn0.05O2 Cathode Materials Doped with Molybdenum Ions for Lithium-Ion Batteries

“…Recently, electric vehicles have already become a reality around the world, so development of power sources, which guarantee their long driving ranges and safety is critically important. Among these power sources, advanced lithium ion batteries (LIBs) are the most appropriate ones for electrochemical propulsion, since they may provide the necessary high energy density, cycle life, stability, and reasonable safety [1][2][3][4][5][6][7][8][9][10][11]. The limiting factor of energy content in LIBs are the positive electrodes (cathodes) and their improvement is much more effective compared to other parts of batteries to get high energy density [12].…”